Kelun-Biotech: How a Chinese IV-Drip Maker's Cast-Off Bet Became Merck's Most Expensive Shopping Trip

I. Introduction & Episode Roadmap

On December 22, 2022, Merck & Co. put out a press release that made the biotech world stop and read it twice. The American pharmaceutical giant had agreed to pay $175 million in cash, up front, to a company that most people outside a few oncology conferences in Shanghai and Chengdu had never heard of. In exchange, Merck received global licenses and options on seven investigational antibody-drug conjugates — cancer drugs. Not one of them had been tested in a human being. And if every one of those seven molecules cleared every hurdle, Merck would owe as much as $9.3 billion in milestone payments, plus tiered royalties on sales.¹

Trade press reached for the same adjective. FierceBiotech called it an "eye-popping" blank check.² In the calculus of biobucks — the industry's habit of publishing the theoretical maximum value of a licensing deal as though it were a purchase price — this was, at signing, among the largest agreements the industry had ever produced. For preclinical assets. From a company incorporated six years earlier as an internal research unit of a Chinese maker of intravenous saline bags.

That company is 四川科伦博泰生物医药 Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd., known as 科伦博泰 Kelun-Biotech, listed on the Hong Kong Stock Exchange under the code 6990. It develops antibody-drug conjugates, or ADCs — a class of cancer medicine that has become the single hottest modality in oncology and, not coincidentally, the field in which Chinese biotechnology has moved fastest from imitation to genuine originality.

The question this story exists to answer is not whether Kelun-Biotech has been successful — by several measures it plainly has, with four products and eight approved indications in China and a first half-year of profit reported in August 2026. The question is harder and more useful: is this a genuine platform company that solved something real about ADC chemistry, or is it the best-placed beneficiary of a broader gold rush in which Western pharmaceutical companies, desperate for oncology growth, are buying cheap options on unproven Chinese science at industrial scale? Those two explanations produce very different long-run economics, and the evidence is genuinely mixed.

The path runs like this. First, the cash cow — a low-margin generics and infusion-solutions business in Sichuan that funded a moonshot. Then the platform bet, made in 2016 when ADCs were still a niche with a handful of approved drugs. Then the Merck deals, three of them in eight months, and the Hong Kong listing that monetized the halo. Then the part most write-ups skip: what actually happened to those seven candidates. Then the battlefield — TROP2, where Kelun's lead molecule fights Gilead and AstraZeneca for the largest patient population in the class. Then the money, the people, and an honest accounting of what could break the case.

Start where the money came from.

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II. Origins: The Cash Cow That Funded the Moonshot

There is nothing glamorous about intravenous infusion solutions. A large-volume injection bag is mostly water, salt or glucose, sterility, and packaging. It is a commodity with a shelf life, sold by the truckload to hospitals that care primarily about price and reliability of supply. It is, in other words, exactly the kind of business that produces steady cash and no excitement whatsoever.

That was the business 刘革新 Liu Gexin built. He founded 四川科伦药业 Sichuan Kelun Pharmaceutical in Chengdu in 1996, and over the following decade and a half turned it into one of China's largest manufacturers of IV solutions, alongside a broad portfolio of small-volume injections, sterile powders, antibiotic intermediates, active pharmaceutical ingredients, and packaging materials.³ The company listed on the Shenzhen Stock Exchange in 2010 under the code 002422, and by 2023 was generating operating revenue of roughly RMB21.5 billion and net profit of about RMB2.46 billion — a real industrial enterprise, not a startup.³

But the cash flows underneath were under structural attack. Beginning in 2018, China's 带量采购 volume-based procurement regime — centralized national tenders in which manufacturers bid for guaranteed hospital volumes — began systematically stripping price out of off-patent drugs. Winners got scale; everyone got margin compression. For a company whose economics rested on high-volume, low-differentiation manufacturing, the message from Beijing was unambiguous: the generic business would keep the lights on, but it would not compound.

Every large Chinese pharmaceutical group read the same memo at roughly the same time. 恒瑞医药 Hengrui Pharmaceuticals, the country's largest domestic drugmaker by revenue, pivoted from generics to innovative oncology. 百济神州 BeiGene built a research organization designed from the start for global trials. The generics-to-innovation transition became the defining strategic move of Chinese pharma in the late 2010s.

What distinguished Kelun's version was the structure. Rather than acquiring an innovation platform — the fast, expensive, and frequently value-destroying route — Liu chose to build one internally and keep it separate. Kelun-Biotech was established in 2016 as the group's dedicated innovative-drug arm, and it was incubated inside the parent for roughly six years before it took a single dollar of external capital.

It is worth sitting with how that decision looked at the time, because hindsight flatters it enormously. In 2016, antibody-drug conjugates were a modality with a troubled history and a thin commercial record. The concept — attach a cytotoxic payload to a targeting antibody so the poison goes where the tumor is — dated to the 1980s. Two decades of attempts had produced a graveyard of failures and, by the mid-2010s, only a small number of approved products worldwide, principally Kadcyla and Adcetris. The chemistry was unforgiving: linkers that broke too early poisoned healthy tissue; linkers that never broke delivered nothing. Manufacturing was hard. Toxicity was hard.

So the capital-allocation decision reads, stripped of narrative: a founder took cash generated by selling saline bags into a price-controlled hospital system, and directed it into one of the most technically difficult and commercially unproven modalities in oncology, with no external validation and no visible exit for six years. That is either patient capital or an expensive hobby, and the only honest way to judge it is against outcomes — which is what the rest of this story does.

One structural note that will matter later. Because Kelun-Biotech was grown inside the parent rather than bought, the parent's ownership was never diluted by an acquisition premium, and the two entities remained entangled in manufacturing, intellectual property, and supply arrangements. That entanglement produced a controlled-company structure and a continuing set of related-party transactions that persist to this day — a governance feature, not an accident, and one an investor has to price.

What the money bought was a platform, and a bet on a single molecule.

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III. Building OptiDC: The Platform Bet

Explaining an antibody-drug conjugate to a non-specialist usually starts with the same analogy, and it is a good one: chemotherapy is carpet bombing, and an ADC is a guided munition. The antibody is the guidance system — it recognizes a protein that sits on the surface of tumor cells. The payload is the warhead — a cytotoxic compound far too poisonous to inject on its own. The linker is the mechanism that holds them together in the bloodstream and releases the warhead once the package has been pulled inside the cancer cell.

Almost all of the engineering difficulty lives in the linker and in one deceptively simple number: the drug-to-antibody ratio, or DAR — how many payload molecules are attached to each antibody. Load too few and the drug is weak. Load too many and the molecule becomes unstable, clears too fast from the body, and dumps its payload in the wrong places. And because conjugation chemistry is messy, most ADCs are not one molecule but a distribution — a mixture of antibodies carrying different numbers of payloads, with different behavior. Controlling that distribution precisely, at every site you intend and no others, is the difference between a laboratory result and a medicine.

Kelun-Biotech's answer is a platform it calls OptiDC. The company's technical claims are specific: proprietary linker chemistry and site-specific conjugation, payload diversity extending beyond the tubulin and topoisomerase inhibitors that dominate the field, and tight control of DAR. In its lead molecule, that control produced a DAR of 7.4 — roughly double the DAR of 4.0 carried by the deruxtecan-based ADCs from 第一三共 Daiichi Sankyo, which means substantially more payload delivered per antibody that reaches a tumor.⁴ The company has since extended the platform toward dual-payload ADCs, bispecific and biparatopic antibody conjugates, and radionuclide-drug conjugates, with its first radionuclide candidate, SKB107, entering clinical trials.⁵

The claim to interrogate is whether OptiDC constitutes differentiated chemistry or a well-executed assembly of components already validated by Seagen, Daiichi Sankyo, and Immunomedics. Both readings survive contact with the evidence.

In favor of differentiation: the linker and payload genuinely are not copies. The published description of the lead molecule's construction identifies a novel linker built on 2-methylsulfonyl pyrimidine chemistry, carrying a belotecan-derived topoisomerase I inhibitor — a payload lineage distinct from both the SN-38 used in Gilead's Trodelvy and the deruxtecan used by Daiichi Sankyo.⁴ More persuasively, the platform has produced two internally discovered, independently approved ADCs in China, which is a genuinely short list among Chinese ADC developers, most of whom have licensed out assets but never taken one through a regulator themselves.

Against: as of this writing, no head-to-head randomized trial has ever compared an OptiDC molecule with a competitor's ADC. Every comparison in circulation — including the ones the company makes on its earnings calls — is cross-trial, drawn from studies with different patient populations, different prior-therapy histories, different geographies, and different monitoring intensity for adverse events. Cross-trial comparison is the weakest form of clinical evidence, and oncology is full of chemistry stories that looked superior on paper and converged toward the field in practice. The chemistry argument is plausible. It is not proven.

By 2021 the platform had converged on a single molecule as its identity: SKB264, a TROP2-directed ADC that would later be named sacituzumab tirumotecan, or sac-TMT. TROP2 is a protein expressed broadly across epithelial tumors — breast, lung, and others — which makes it one of the largest addressable targets in oncology and, for exactly that reason, one of the most crowded.

Going into 2022, the company was privately held, majority-owned by its parent, and had no approved products. It had a platform, a lead asset in early clinical development, and a story. What it needed was someone credible to validate it.

Merck was about to do that three times in eight months.

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IV. The Merck Inflection: Three Deals in Eight Months

Business development at a company like Merck runs on a simple, brutal arithmetic. Keytruda, its anti-PD-1 antibody, had become one of the best-selling medicines in pharmaceutical history — and its principal patents were headed for expiry at the end of the decade. Everything Merck did in oncology between 2020 and 2025 can be read as an answer to one question: what replaces Keytruda? Antibody-drug conjugates were the most credible answer available, because they combine with checkpoint inhibitors, extend into large solid-tumor populations, and were producing the most striking clinical data in the field.

The problem was supply. The best Western ADC franchises were owned and expensive. Merck had tried and failed to buy Seagen. Which left a route that in 2022 still felt slightly exotic to American boardrooms: license the science out of China.

The relationship began in May 2022, when Kelun-Biotech announced an oncology research collaboration and exclusive license agreement with Merck.⁶ The asset was SKB264 — the TROP2 ADC, which inside Merck's development machine acquired the designation MK-2870. The terms were modest by the standard of what followed: roughly $47 million up front, with up to approximately $1.4 billion in potential milestones. What mattered was less the money than the signal. A top-five global pharmaceutical company had run diligence on a Chinese preclinical-to-early-clinical ADC and concluded it was worth developing.

In July 2022 came the second deal — $35 million up front and up to roughly $900 million in milestones for a second, then-undisclosed ADC candidate.⁷ Two deals with the same partner inside three months is not a coincidence; it is a signal that the diligence team liked what it saw the first time and went back for the platform rather than the molecule.

Then December 2022, and the agreement that changed the company's life. Merck took exclusive global licenses and options across seven investigational preclinical ADC candidates. The consideration: $175 million in cash up front, tiered royalties on net sales, and up to $9.3 billion in aggregate development, regulatory, and sales milestones — a figure that, as Merck's own release carefully specified, assumed that Kelun-Biotech forwent its Greater China rights on the option assets and that every single candidate achieved regulatory approval.¹ Merck received rights globally; Kelun-Biotech retained development and commercialization rights for mainland China, Hong Kong, and Macau on certain of the licensed and option ADCs.¹

Alongside the license, Merck put money into the equity. It participated in a $200 million Series B financing, contributing half, and emerged owning roughly 6.95% of Kelun-Biotech ahead of the IPO — the second-largest shareholder behind the parent.⁸ Merck's Dr. Dean Y. Li framed the rationale in the language of modality rather than molecule: advances in ADC technology, he said, were yielding "a new generation of candidates designed to precisely target and deliver potent anticancer agents."¹ Kelun-Biotech's chief executive, 葛均友 Ge Junyou, called the partnership "strong endorsement for our technology from a cancer treatment leader."¹

Add the three agreements together and the headline exposure across 2022 approached $11.8 billion in potential milestones plus royalties. This is the moment to be precise about what that number is, because almost every popular account of this company gets it wrong.

Biobucks are a ceiling, not a forecast. A licensing headline is the arithmetic sum of every payment that would become due if every asset in the agreement succeeded at every stage — preclinical, each phase of clinical development, each regulatory filing in each territory, and then each sales threshold, often stretching into multi-billion-dollar annual revenue tiers that fewer than fifty drugs in history have reached. Applied to seven preclinical molecules, in a field where the historical probability of a preclinical oncology candidate reaching approval sits in the low single digits, the expected value of a $9.3 billion ceiling is a small fraction of the ceiling. The cash actually received on signature — $175 million — is the only number in the announcement that was contractually certain.

That said, the up-front number is itself informative when benchmarked. In August 2021, Seagen had licensed 荣昌生物 RemeGen's HER2 ADC disitamab vedotin for $200 million up front and up to $2.4 billion in milestones — a large deal, but for a single asset already in the clinic.⁹ In April 2023, BioNTech licensed two ADCs from 映恩生物 DualityBio for $170 million up front and more than $1.5 billion in milestones, expanding to a third asset later that year.[^10] Even the later multi-asset benchmarks stayed in a similar band: in July 2025, GSK agreed to pay 恒瑞医药 Hengrui $500 million up front across as many as twelve programs spanning respiratory, immunology, and oncology, with roughly $12 billion in potential milestones.¹⁰

Read against that cohort, Kelun-Biotech's December 2022 agreement stands out on two dimensions: it was earlier than most of the wave, and it was platform-level rather than asset-level — Merck was buying access to a discovery engine, not a molecule. The most defensible conclusion is narrow: in late 2022, a sophisticated acquirer with unusually strong incentives to be right about ADCs looked at Kelun-Biotech's chemistry and paid a top-of-cohort price for optionality on it. That is meaningful evidence about how the platform looked to expert eyes. It is not evidence that the platform works, and the up-front-versus-ceiling gap means it is not even strong evidence about price.

The structure Merck and Kelun-Biotech chose — global rights to the multinational, Greater China retained by the originator — became the template that most subsequent China-ADC licensing deals copied. It solved the two problems that had previously stalled these transactions: the Western partner got clean global commercialization rights, and the Chinese originator kept the domestic market it was actually equipped to sell into.

Nine months later, the company took that validation to the public markets.

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V. Going Public on the Halo

By early 2023, the Merck relationship had done something no amount of preclinical data could have: it made Kelun-Biotech legible to generalist investors. Bloomberg reported in February 2023 that the Merck-backed company had selected banks for a Hong Kong listing.¹¹ The pitch essentially wrote itself. A global pharmaceutical major had validated the science, taken equity, and committed to fund development. Public investors were being offered a seat next to Merck.

The offering opened books at a valuation targeting roughly $208.6 million, with 22.44 million shares marketed in a range of HK$60.60 to HK$72.80 per share.¹² It priced at the bottom of that range. Shares began trading on the Main Board of the Hong Kong Stock Exchange on July 11, 2023, opening at HK$60.60, with net proceeds of approximately HK$1.26 billion assuming exercise of the over-allotment option — at the time the largest biopharmaceutical IPO in Hong Kong in two years.¹³ Five cornerstone investors — RTW Funds, Laurion Capital Master Fund, TruMed, CUAM, and Kelun International — subscribed for roughly $67.3 million of the deal.¹³

Pricing at the bottom of the range is worth a beat. In mid-2023 the Hong Kong biotech market was in poor condition; the post-2021 drawdown in Chinese healthcare equities had been severe, and the pool of investors willing to fund unprofitable biotech had thinned dramatically. That Kelun-Biotech got the deal done at all put it in a small minority. That it got it done at the low end says the Merck halo bought access to the market, not pricing power within it.

The mechanics of how it listed matter as much as the outcome. The offering was structured as a formal spin-off from the Shenzhen-listed parent, executed under the 中国证监会 CSRC's spin-off rules for domestically listed companies — one of the earlier transactions of its type under that regime.¹⁴ The logic behind the wave of such carve-outs is straightforward and mostly sound: an innovation business buried inside a generics manufacturer gets valued on the parent's multiple, cannot issue equity against its own pipeline, and cannot pay biotech-competitive equity compensation to scientists. Separating it creates a currency. It also creates a governance question, since the parent typically retains control.

Which it did here. Post-listing, Kelun Pharmaceutical and affiliated entities retained roughly 68.5% of the company, leaving Kelun-Biotech a controlled company in the technical Hong Kong sense — one shareholder with the votes to determine every ordinary and most special resolutions.¹⁵ Merck's stake made it the largest external holder.

That combination is genuinely unusual, and it cuts both ways. On the constructive side, a licensing partner holding equity is unusually well aligned: Merck's returns depend on Kelun-Biotech's molecules working, and its equity position gives it an additional claim on any value the partnership creates. On the cautious side, an investor buying the free float is buying a minority position in a company where the controlling shareholder is an operating pharmaceutical group with its own manufacturing, intellectual property, and supply relationships with the subsidiary. Continuing connected transactions between the two are a permanent feature of the structure, disclosed and subject to Hong Kong's related-party rules, but structurally present.

There is one small, concrete marker of progress in the listing regime worth recording. Kelun-Biotech listed under Chapter 18A, the Hong Kong Exchange's route for pre-revenue biotech companies, which appends a "B" marker to the stock code as a warning to investors. The exchange subsequently approved removal of that marker — a mechanical consequence of meeting revenue and market-capitalization thresholds, but a real one, and the kind of step most Chapter 18A listings never reach.¹⁶

The halo, though, rested on a specific claim: that Merck's seven-candidate commitment validated the platform. Within three months of the IPO, that claim started getting tested.

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VI. Stress-Testing the Deal: What Happened to the Seven Candidates

On October 20, 2023, Merck announced it had agreed to acquire global rights to 第一三共 Daiichi Sankyo's ADC portfolio in a transaction valued at up to $22 billion, including $4 billion in guaranteed payments. Three days later, on October 23, the trade press reported that Merck had discontinued its exclusive license on one preclinical Kelun-Biotech ADC and declined to exercise its exclusive option on another.¹⁷

The proximity is the story. No official reason was given for the discontinuations, and it is worth stating plainly that the causal link is inference rather than disclosure.¹⁷ But the sequence is hard to ignore: a company that had just committed billions to a rival ADC portfolio trimmed the early-stage assets whose therapeutic areas that portfolio now covered. Kelun-Biotech's response at the time was that it would continue developing the returned assets and seek new collaborators.¹⁷

The attrition continued. In August 2024, Merck exercised its option on SKB571 — a bispecific ADC that Kelun-Biotech has positioned primarily against solid tumors including lung and gastrointestinal cancers — paying $37.5 million and unlocking further downstream milestones. In the same transaction, it handed back global rights to SKB315, a CLDN18.2-directed ADC.¹⁸

Net the ledger, and the picture is clear enough. Of the seven preclinical candidates that generated a $9.3 billion headline in December 2022, several had been returned or declined within two years, and only a minority remained actively licensed. Some were abandoned before ever reaching a human trial.

Now the analytical question: does this falsify the "Merck deal validates the platform" thesis?

The honest answer is that it narrows the thesis rather than rejecting it, and the narrowing is significant. Portfolio attrition at the preclinical stage is normal — indeed, the entire economic point of an option-based multi-asset structure is that the licensee can kill most of the portfolio cheaply. Merck did not walk away. It kept the lead asset, exercised a new option, and paid additional cash to do so. A partner that had lost faith in the underlying chemistry would not have written the SKB571 check.

But the attrition does dispose of the strongest version of the bull case — the one in which a $9.3 billion headline is treated as a proxy for the platform's value. What Merck's behavior actually demonstrates is that it valued specific molecules, evaluated them individually, and discarded the ones that did not fit its portfolio once its portfolio changed. That is a client relationship, not a platform endorsement. The correct way to price Kelun-Biotech's Merck exposure is on the assets Merck retained, the cash actually received, and the milestone payments plausibly reachable on those specific programs — a number that bears no useful relationship to $9.3 billion.

It follows that the platform claim has to be judged on the molecules that reached patients under Kelun-Biotech's own name: sac-TMT, and the HER2 ADC that would follow it. That is an argument the company can actually win, and largely has.

There is a forward test that would resolve the remaining ambiguity, and it is worth naming precisely because it is falsifiable. If Merck exercises additional options, or signs a genuinely new platform-level agreement with Kelun-Biotech over the next two to three years, the platform claim survives in something close to its original form. If the relationship instead continues quietly narrowing to sac-TMT alone, with no new deals, the correct conclusion is that Kelun-Biotech is a very good single-molecule company that once sold a portfolio option — a materially less valuable proposition, and one that ties the entire equity story to a single molecule's performance in a crowded field.

Which is exactly where the fight is.

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VII. The Core Business: Industry Structure & the TROP2 Battlefield

Why the whole industry pivoted to ADCs

For about thirty years, the guided-munition idea stayed mostly theoretical. The turning point was not a concept but a data set. When 第一三共 Daiichi Sankyo and AstraZeneca reported results for Enhertu, their HER2-directed ADC, in heavily pretreated breast cancer patients, the response rates were of a magnitude oncologists associate with the first generation of a genuinely new modality rather than an incremental improvement. Then Enhertu worked in tumors with only low HER2 expression — patients previously considered HER2-negative and therefore ineligible for HER2-directed therapy. That result did something subtle and important: it decoupled the payload's effect from the target's abundance. If a well-designed conjugate could work at low antigen expression, the addressable population for every ADC target expanded, sometimes by multiples.

Two consequences followed immediately. First, every large pharmaceutical company needed an ADC franchise, and there were not enough good ones to go around. Second, attention moved to whichever antigen was expressed most broadly across the most patients.

TROP2: the largest prize, and the most crowded arena

That antigen is TROP2. It is expressed across a wide range of epithelial tumors — breast cancer of multiple subtypes, non-small cell lung cancer, and others — which makes it, in commercial terms, the biggest addressable population in the ADC field. Three serious programs are contesting it.

Gilead, via Trodelvy. The first-mover. Gilead acquired Immunomedics for approximately $21 billion in 2020 to obtain sacituzumab govitecan, the first approved TROP2 ADC, and built positions in metastatic triple-negative breast cancer and HR-positive/HER2-negative breast cancer. The commercial reality of that franchise is instructive for anyone modeling TROP2 economics: Trodelvy generated roughly $1.4 billion in full-year 2025 sales, up 6% year on year, with growth from breast cancer demand partly offset by the withdrawal of its bladder cancer indication.¹⁹ A first-in-class TROP2 ADC, five years post-approval, is a solid $1.4 billion product growing at single digits — not the $5 billion blockbuster the acquisition price implied. That is the base rate against which every TROP2 forecast should be sanity-checked.

AstraZeneca and 第一三共 Daiichi Sankyo, via Datroway. The second mover, built on the same deruxtecan linker-payload chemistry that made Enhertu work, with a TROPION development program spanning breast and lung cancer. Datroway won its first FDA approval in breast cancer and subsequently, in June 2025, in EGFR-mutated non-small cell lung cancer after prior targeted and platinum-based therapy.²⁰ Its differentiating problem is safety: the deruxtecan platform carries a well-documented signal for interstitial lung disease, an inflammation of lung tissue that can be fatal, and which requires active monitoring and dose interruption in practice.

Kelun-Biotech and Merck, via sac-TMT. The third entrant, and the first non-Western TROP2 ADC to reach approval anywhere. The chemistry differences described earlier — the 2-methylsulfonyl pyrimidine linker, the belotecan-derived topoisomerase I payload, and the DAR of 7.4 versus 4.0 for the deruxtecan conjugates — are the basis of the company's differentiation claim.⁴

What the clinical evidence actually shows

The registrational study in China was OptiTROP-Breast01, a randomized Phase 3 trial in previously treated advanced triple-negative breast cancer, which supported the first NMPA approval in November 2024 for patients who had received at least two prior systemic therapies — the first domestically developed TROP2 ADC, and the first domestically developed ADC granted full approval, in China.²¹ In the updated analysis published in April 2025, sac-TMT produced median progression-free survival of 6.7 months against 2.5 months for chemotherapy, with a hazard ratio of 0.32, an overall response rate of 45.4% versus 12%, and median overall survival not yet reached against 9.4 months for the comparator.⁴

Those are strong numbers. They are also, critically, numbers against physician's-choice chemotherapy in a Chinese patient population — not against Trodelvy. On a cross-trial basis, sac-TMT's pivotal data sit competitive with, not clearly superior to, the TROP2 incumbent's own registrational results. The differences in trial populations, prior-therapy burden, and standard of care between a Chinese third-line trial and a Western third-line trial are large enough that the honest verdict is: comparable, unproven either way.

Where the evidence is more interesting is safety. The published characterization of sac-TMT's profile notes no reported interstitial lung disease or pneumonitis to date and an absence of the significant gastrointestinal toxicity that constrains Trodelvy dosing, with toxicity instead concentrated in blood counts — as expected from a belotecan-derived payload — and stomatitis as the distinctive adverse event.⁴ Grade 3/4 neutropenia in the pivotal trial ran at 34.6% versus 47.0% on chemotherapy.⁴ Datopotamab deruxtecan, by contrast, shows milder hematologic toxicity but carries the ILD signal.⁴

This is the most credible version of Kelun-Biotech's differentiation argument, and it deserves to be stated carefully. A more stable linker plausibly means less payload released in circulation, which plausibly means less off-target damage. The absence of ILD in reported data is a real and clinically meaningful differentiator if it holds. But "no ILD reported to date" is a statement about a bounded set of trials with a specific monitoring protocol and a specific population, and ILD is precisely the kind of adverse event that surfaces at scale, in older and sicker post-approval populations, after the controlled trials are over. Treat it as a promising early signal, not an established property of the molecule.

The frontier: first-line lung cancer

Second- and third-line indications are where ADCs get approved. First-line is where they become large businesses, because first-line is where the patients are. The frontier fight is therefore ADC-plus-checkpoint-inhibitor combinations in newly diagnosed advanced lung cancer, and this is where Kelun-Biotech's data flow in 2025 and 2026 has been genuinely notable.

The company reported that OptiTROP-Lung05, testing sac-TMT plus pembrolizumab against pembrolizumab alone in first-line PD-L1-positive advanced NSCLC, met its primary endpoint with a statistically significant improvement in progression-free survival — the first Phase 3 trial of an ADC combined with a checkpoint inhibitor to hit its primary endpoint in first-line NSCLC.²² It then reported that OptiTROP-Lung06, testing the same combination against chemotherapy plus pembrolizumab in first-line PD-L1-negative non-squamous NSCLC, also met its PFS endpoint at a prespecified interim analysis, with a positive trend in overall survival and no new safety signals.²³

Taken together, those two readouts cover both sides of the PD-L1 biomarker split — which is what the company's chief medical officer meant on the August 2026 interim results call in saying that "whether it's PD-L1 negative or positive, we cover them all."²⁴ Merck, for its part, has taken the molecule into a global program that Kelun-Biotech describes as seventeen ongoing Phase 3 studies across lung, breast, gynecological, gastric, and urinary cancers.⁵

The competitive race is against AstraZeneca and Daiichi Sankyo's TROPION-Lung10, which pairs datopotamab deruxtecan with the bispecific rilvegostomig against pembrolizumab in treatment-naive non-squamous NSCLC with high PD-L1 expression; readouts from that study are expected after 2026.²⁵ Whoever converts first-line combination data into first-line approvals first captures the largest population in the class. This is the single most consequential catalyst in the story, and it cuts both ways: Kelun-Biotech is currently ahead on published Phase 3 endpoint hits, but PFS is not survival, Chinese registrational trials are not global registrational trials, and the population that matters commercially in the West will be adjudicated by Merck's own studies, not Kelun's.

The rest of the Chinese ADC field

RemeGen and DualityBio are real competitors and useful deal comparables, but neither is a like-for-like rival at the platform level: RemeGen's flagship licensing arrangement covered a single HER2 ADC, and DualityBio's BioNTech agreements covered two and then three assets.⁹[^10] MediLink Therapeutics belongs in a different category entirely, for reasons the litigation section will make clear. What separates Kelun-Biotech from the cohort is not deal count but the fact that it has taken its own molecules through a regulator and put a commercial organization behind them.

Industry structure: why this is happening at all

China's biopharmaceutical out-licensing volume has gone from significant to structurally important. Cross-border licensing by Chinese drugmakers reached roughly $136 billion in announced transaction value in 2025 — close to triple the prior year's level — with ADCs the single largest therapeutic category by value, and Chinese originators accounting for the overwhelming majority of global ADC licensing activity.²⁶ The trade press had already flagged the trend as "scorching hot" and asked, reasonably, whether geopolitics would eventually rain on it.²⁷

The mechanism behind the boom is not mysterious. China produced, over roughly fifteen years, an enormous cohort of Western-trained medicinal chemists and clinical developers, a domestic clinical-trial system that can enroll patients faster and far more cheaply than the US or EU, and a regulatory regime that rewards domestic innovation. Western pharmaceutical companies face patent cliffs and need assets. Chinese biotechs have assets and cannot fund global Phase 3 programs. The trade is obvious once both sides admit it.

Kelun-Biotech's December 2022 agreement predates most of this wave, which supports a limited but genuine claim: it was an early mover in the "China innovation, Western commercialization" model rather than a late follower.

Five Forces and 7 Powers, applied honestly

Run the industry structure and the picture is less flattering than the growth numbers suggest.

Buyer power is high and highly concentrated. The realistic buyers of a China-originated ADC are a handful of global majors — Merck, AstraZeneca, Pfizer, BMS, GSK, and a few others. They compete with one another for access, which supports headline valuations, but each individually holds enormous leverage over terms, milestone structures, and the right to walk away. Merck's 2023 and 2024 discontinuations are the demonstration.

Substitution is real and rising. Bispecific antibodies, T-cell engagers, cell therapies, and next-generation payload chemistries all compete for the same oncology dollars. Within TROP2 specifically, the threat is more acute: three approved or near-approved molecules chasing overlapping populations tends to produce price competition, and in China it produces something more severe than price competition, which is the reimbursement negotiation described below.

Rivalry within TROP2 is intense and getting worse, with all three players pushing into first-line simultaneously.

Supplier power is low — Kelun-Biotech manufactures its own biologics and benefits from the parent group's industrial base.

On Hamilton Helmer's 7 Powers, the honest assessment is that Kelun-Biotech's advantages are cost- and process-based rather than structural. There is a plausible process power claim in the OptiDC chemistry, if the linker stability advantage proves durable and difficult to replicate. There is a genuine cost advantage in Chinese discovery and clinical development that is real but shared with every domestic competitor and therefore not proprietary. There is first-mover position in China's TROP2 market, which is a beachhead rather than a moat. What is conspicuously absent is any evidence of a defensible intellectual property fortress: no branded patent-litigation moat has been identified for Kelun-Biotech in the TROP2 space, and the one significant IP dispute in the company's record ran the other direction, as a trade-secret claim it brought and settled.

The practical implication for an investor is that the durable question is not whether sac-TMT gets approved in more indications — it clearly will — but whether the franchise holds price and share once the Chinese reimbursement system and two well-funded Western competitors have finished working on it.

Approvals, though, came first.

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VIII. From Platform to Pharmacy: Approvals and the Profitability Inflection

In November 2024, something changed in the nature of the company. Until that month, Kelun-Biotech was an R&D organization that monetized science by selling it to foreigners. Then China's 国家药品监督管理局 National Medical Products Administration approved sacituzumab tirumotecan for patients with unresectable locally advanced or metastatic triple-negative breast cancer who had received at least two prior systemic therapies, and Kelun-Biotech became a company that sells medicine to hospitals.²¹

The distinction matters more than it sounds. Licensing income is lumpy, non-recurring, and controlled by a counterparty. Product revenue compounds, builds an installed base of prescribers, and belongs to you. Everything in the company's financial profile since 2024 has been driven by the shift from the first kind of revenue to the second.

The approvals came in sequence and quickly. In January 2025, tagitanlimab — the company's PD-L1 antibody, formerly A167, and not an ADC — was approved in combination with cisplatin and gemcitabine for the first-line treatment of nasopharyngeal carcinoma, which the company described as the first PD-L1 monoclonal antibody globally authorized for that use.²⁸ Cetuximab N01 also received initial marketing approval during the year.²⁸

Then October 2025 produced two approvals in the same month, and they were the important ones.

On October 11, the NMPA approved sac-TMT for adults with EGFR mutation-positive locally advanced or metastatic non-squamous NSCLC who had progressed after EGFR-TKI therapy.²⁹ The registrational study, OptiTROP-Lung04, compared sac-TMT monotherapy against pemetrexed plus platinum chemotherapy and showed statistically significant and clinically meaningful improvements in both overall survival and progression-free survival; it was selected as a late-breaking abstract for the Presidential Symposium at the 2025 ESMO Congress.²⁹ The company's characterization — the first and only ADC globally to demonstrate an overall survival benefit versus platinum doublet chemotherapy in advanced NSCLC progressing after TKI therapy alone, and the first TROP2 ADC approved in lung cancer anywhere — is a claim about approval sequence, and appears accurate as stated.²⁹

The substance underneath the superlative is what counts. An overall survival benefit is the gold standard endpoint in oncology, because unlike progression-free survival it cannot be manufactured by imaging schedules or subjective assessment. Patients on the drug lived longer. Whatever one concludes about linker chemistry, that result is not a cross-trial inference.

Later the same month, trastuzumab botidotin — the HER2 ADC formerly known as A166 — was approved for adults with HER2-positive breast cancer who had received one or more prior anti-HER2 therapies, the first domestically developed HER2 ADC approved in that setting in China.³⁰ With that, the single-molecule identity was gone. Sac-TMT went on to receive a fourth Chinese indication in HR-positive/HER2-negative breast cancer, giving Kelun-Biotech four commercialized products across eight approved indications by the end of 2025.²⁸

Regulatory approval, however, is not commercialization, and in China there is a second gate that determines whether an approval becomes a business: the 国家医保药品目录 National Reimbursement Drug List. Three of Kelun-Biotech's products, covering five indications, were included in the 2025 NRDL with effect from January 1, 2026.²⁸ Inclusion delivers volume — hospital access, insurance coverage, and a dramatic drop in the patient's out-of-pocket cost. It also delivers a price cut, negotiated annually, and the negotiations are not gentle. This is the structural reason why Chinese oncology franchises scale in units far faster than in yuan, and why any model of Kelun-Biotech's domestic revenue has to assume that per-patient economics erode as volume grows.

That trade-off is visible in the numbers the company reported for the first half of 2026.

Revenue was RMB978.3 million, up only about 3% year on year — a flat headline that conceals a violent change in composition.³¹ Sales of pharmaceutical products reached RMB657 million, up 112%, and accounted for roughly 67% of total revenue.³¹ In other words, product sales more than doubled while total revenue barely moved, which means collaboration and licensing revenue fell by a comparable amount. That is exactly what a transition from a licensing model to a commercial model looks like in the accounts, and it is the reason a single half-year's total revenue growth rate is a nearly useless metric for this company.

And for the first time, Kelun-Biotech reported a profit: net profit of RMB388.0 million against a loss in the prior-year period, with adjusted net profit of RMB479 million and a gross margin above 75%.³¹³²

Here is where the analysis has to be blunt about earnings quality. That profit is not clean. In June 2026 the company received a RMB700 million one-off settlement payment arising from its litigation against MediLink Therapeutics, and management discussed it on the interim results call as a distinct, non-recurring item.³² Against a reported net profit of RMB388 million, a RMB700 million one-time receipt is larger than the entire profit. The correct reading is that Kelun-Biotech's underlying operations remained loss-making in the first half of 2026, and that the reported swing to profit was made possible by a legal settlement.

That does not make the operating progress fake. Product sales genuinely doubled. Gross margin is genuinely high. The commercial organization has genuinely scaled — approximately 2,300 employees in total, of whom more than 800 sit in commercialization, covering roughly 2,000 hospitals across thirty provinces, up from a commercial team of about 600 covering 1,200 institutions a year earlier.³¹³³ Management told investors on the August 2026 call that full-year 2026 commercialization revenue should at least double the 2025 level, and framed sustainable break-even as achievable in the 2026 to 2027 window.³¹

But the distinction between "we became profitable" and "we received a settlement that exceeded our operating loss" is the whole ballgame for an investor trying to determine whether this business has crossed an inflection or approached one. Two consecutive halves of profit driven by product sales, with no one-off items, would settle it. One half does not.

The capital that funded all of this deserves its own examination, because it has been raised repeatedly.

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IX. Money In, Money Out: Financials and Capital Allocation

The arc of Kelun-Biotech's revenue since listing looks, at a glance, like steady progress: approximately RMB1.54 billion in 2023, RMB1,933 million in 2024 for growth of 25.5%, and RMB2,057.9 million in 2025 for growth of about 6.5%.³⁴²⁸ Look at the composition and the arc is not steady at all — it is one revenue stream decaying and another being built underneath it.

The early years were dominated by license and milestone income from Merck, which arrives in irregular chunks triggered by contractual events rather than by operations. Roughly $90 million of such income landed in a single half-year in 2024. Product revenue, by contrast, barely existed until 2025, when commercialized product sales reached about RMB540 million, and then more than doubled in the first half of 2026 alone.³³³¹ For a company in this transition, year-on-year total revenue growth is close to meaningless. The number that carries information is product sales.

The profit-and-loss history is where the popular narrative needs correcting. It is often said that Kelun-Biotech's losses narrowed steadily until the 2026 breakthrough. They did not. The reported net loss was approximately RMB266.8 million in 2024, and then widened to RMB381.97 million in 2025 — the loss got bigger in the year before the swing to profit, not smaller.³⁴²⁸ On an adjusted basis excluding equity-settled share-based payments, the 2024 loss was about RMB118.5 million and the 2025 loss about RMB211.3 million, so the widening holds on both measures.³⁴²⁸

The reason is not deterioration; it is the cost of building a commercial organization. Selling and distribution expenses rose roughly 160% in 2025 to about RMB475 million as the company hired a field force and launched into hospitals for the first time.³³ Research and development spending rose to RMB1,319.7 million in 2025 and then rose a further 25.7% year on year to RMB768 million in the first half of 2026 alone.²⁸³¹ This is a company still spending ahead of its revenue by design, not harvesting.

Whether that is discipline or drift depends entirely on conversion, and the honest answer today is that the conversion evidence is early but real: four products, eight indications, NRDL inclusion, and product sales doubling. That is a better record than most of the Chinese biotech cohort can show. It is also only about eighteen months old.

The balance sheet is genuinely strong. Cash and financial assets stood at approximately RMB4.56 billion at the end of 2025 and RMB4.78 billion at the end of June 2026, with a debt-to-asset ratio of 18.7% at year-end 2025 that management characterized on the results call as very healthy.²⁸³¹³³

Which brings up the item a skeptical investor would push hardest on. Kelun-Biotech has returned to the equity market three times since its IPO, each time at a discount, while holding a large cash balance.

The first was an H-share placing in May 2024.³⁵ The second, in June 2025, raised approximately $250 million.³⁶ The third, and largest, came in July 2026: on July 8 the company agreed to place roughly 5.84 million new H-shares at HK$470.20 each — a discount of about 8.5% to the prior close of HK$514 — with Goldman Sachs, Citigroup, and JPMorgan as joint bookrunners, generating net proceeds of approximately HK$2.72 billion, stated as intended for R&D, clinical trials, manufacturing, commercialization, and general working capital.³⁷⁵

Three discounted placements in a little over three years, from a company sitting on RMB4.5 billion of cash and reporting a profit, is a pattern rather than an event, and it deserves to be read on its own terms rather than accepted at management's framing. There are two credible interpretations. The charitable one is opportunistic financing: the shares appreciated enormously between 2023 and 2026, and issuing equity into strength to fund seventeen global Phase 3 trials and a commercial buildout is textbook capital management for a biotech that expects to spend heavily for years. The less charitable one is that a company whose operating cash generation is not yet self-sustaining has become a habitual issuer, and that each discounted placement transfers value from existing holders to new ones at a price management has judged attractive to sell at.

The evidence does not cleanly select between them. What can be said is that the "large cash balance" argument for capital discipline is weaker than it looks, because a substantial portion of that balance has been parked in bank wealth-management products — the company disclosed RMB1.5 billion of outstanding principal across products from Industrial Bank, CZB, CMB, and CITIC in a May 2025 announcement, describing the purpose as optimizing asset management and liquidity.³⁸ This is an extremely common practice among cash-rich China-linked issuers and is not, on the current evidence, a governance problem. It is a watch item: a company simultaneously raising equity at a discount and deploying idle cash into structured bank products is making an implicit statement about its own cost of capital that investors are entitled to test on the next earnings call.

Kelun-Biotech pays no dividend and has conducted no buybacks. For a business with this reinvestment profile, that is the correct posture; returning capital while running a seventeen-trial global program and building a national sales force would be strange. The discipline question is not about distributions. It is about issuance.

Worth noting alongside the Merck relationship: the company has demonstrated it can sell science to counterparties other than Merck. In January 2025, Kelun-Biotech and Harbour BioMed licensed HBM9378/SKB378, an anti-TSLP fully human monoclonal antibody for immunological diseases, to Windward Bio for territories excluding Greater China and several Southeast and West Asian countries — $45 million in upfront and near-term payments including cash and equity, up to $970 million in total potential consideration, plus tiered royalties.³⁹ The amounts are small relative to the Merck agreements, but the transaction matters as evidence: the out-licensing engine is not a single-customer phenomenon, and it now reaches outside oncology.

Behind the capital decisions sit the people making them.

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X. Who's Running It Now

In February 2023, five months before the Hong Kong listing, Kelun-Biotech redesignated its chairman. 刘革新 Liu Gexin — the man who founded the parent company in 1996, built the IV-solutions business, joined the Kelun-Biotech board in 2016 and chaired it from 2022 — moved from an executive role to Non-Executive Director.¹⁵

Pre-IPO governance cleanups are routine, and it would be easy to file this one under housekeeping. It is worth pausing on anyway, because founder-chairmen of Chinese industrial groups do not usually volunteer to step back from operational authority over their most valuable asset. The redesignation separated the founder's board authority from day-to-day executive control at precisely the moment external shareholders were being invited in. Read charitably, it signals that the company intended to be run by its operators rather than by its parent. Read cautiously, it is a formality that changes nothing about who controls roughly 68.5% of the votes.¹⁵ Both readings are defensible; the governance question that actually matters is not who chairs the board but who owns it.

Liu himself is a figure of some prominence in Chinese business — Forbes tracks him as a billionaire on the strength of the Kelun group — but the useful biographical fact for this story is narrower and more revealing than any profile. He spent roughly two decades building a business whose competitive advantage was manufacturing scale in a commodity product, and then directed its cash flow into a research organization whose competitive advantage would have to be chemistry. Those are not adjacent skill sets, and the standard outcome of that pivot in any industry is failure. The specific decision to incubate rather than acquire — accepting six years of invisible spending rather than buying a platform at a premium — is the one capital-allocation call in this company's history that has a clean, favorable verdict, and it belongs to him.

Day-to-day leadership sits with 葛均友 Ge Junyou, Executive Director, Chief Executive Officer, and General Manager, who has been the public face of the company since the Merck deals. He is the executive who described the Merck partnership as an endorsement of the technology in 2022, and he is the one now accountable for a very different job: converting a licensing story into a commercial one.¹

Public biographical material on Ge outside company filings is thin, which is worth stating plainly rather than filling with speculation. What is available is his behavior on earnings calls, and that is the more useful evidence anyway.

Testing management credibility means comparing what they said against what happened. On the 2025 annual results call, Ge described a commercial organization covering more than 300 cities and 1,200 medical institutions with a team of nearly 600, and told investors the commercialization team would exceed 800 personnel and that revenue would roughly double in 2026, with NRDL-covered products representing more than 80% of revenue by year-end.³³ Six months later, at the interim results, the reported figures were more than 800 commercial staff, roughly 2,000 hospitals across thirty provinces, and product sales up 112%.³¹ The headcount and coverage targets were met. The revenue trajectory is on pace against a guide that management reiterated rather than revised.

That is a short track record — two calls — but it is a consistent one, and consistency of narrative is measurable in a way that vision statements are not. The strategic framing has also held: on both calls management described the same "dual-engine" model of out-licensing collaboration plus domestic commercialization, rather than reinventing the story to fit the quarter. Management's language on the interim call was that commercialization momentum is producing "a major change in the business structure" — a claim the composition of H1 2026 revenue actually supports.³¹

Where management is less forthcoming is on the two items an activist would press. First, the settlement gain: the RMB700 million MediLink receipt is discussed, but the reported profit figure is presented in headlines without the operating loss underneath it made equally prominent — a framing choice, not a misstatement. Second, the placements: the stated use of proceeds is generic, and no call has produced a detailed explanation of why a company with RMB4.5 billion of cash and RMB1.5 billion parked in wealth-management products needed to issue equity at a discount three times.³⁸³⁷ That question has an answer; it has simply not been given in detail publicly.

On the capital-allocation record more broadly, a bounded observation: reviewing the company's 2024 and 2025 annual results announcements and 2026 interim results announcement, no failed acquisition, shuttered venture, goodwill impairment, or material write-off is disclosed, and no qualified audit opinion or going-concern emphasis appears.³⁴²⁸⁵ That is a statement about those specific filings over that specific period, not a general assurance. It also reflects a company that is only three years public and has made essentially no acquisitions — a clean record produced partly by an absence of opportunities to get things wrong.

The ownership structure is the governance fact that dominates everything else. Kelun Pharmaceutical and affiliated entities hold roughly 68.5%; Merck is the largest external holder from its pre-IPO 6.95% position.¹⁵⁸ Continuing connected transactions between Kelun-Biotech and the parent group — manufacturing, intellectual property, and supply arrangements — are a permanent structural feature and are disclosed under Hong Kong's connected-transaction rules. Nothing in the public record reviewed here suggests these arrangements have been abusive. But a minority shareholder in this structure has essentially no mechanism to challenge them, and the relevant analytical point is not that something has gone wrong but that the protection against it going wrong is disclosure and regulation rather than voting power.

The single strongest piece of evidence for management credibility is not anything management has said. It is that a counterparty as sophisticated and as well-resourced as Merck — a firm that has demonstrated a complete willingness to hand assets back when they stop fitting — has kept expanding rather than exiting the relationship, and has taken sac-TMT into seventeen global Phase 3 studies.⁵ That is a costly signal from an informed party, and it carries more weight than any management assertion. It is also, importantly, a signal about one molecule.

Which sets up the argument in full.

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XI. Bull vs. Bear: Stress-Testing the Investment Case

The case for

Strip the story to its load-bearing elements and the bull case is more concrete than most biotech bull cases.

A company that did not exist in 2015 now has four commercialized products across eight approved indications in China, three of them in the national reimbursement catalog, sold by an 800-person field organization into 2,000 hospitals.²⁸³¹ Two of those products are antibody-drug conjugates it discovered itself — the first domestically developed TROP2 ADC and the first domestically developed HER2 ADC approved in their respective Chinese settings.²¹³⁰ Its lead molecule produced an overall survival benefit against platinum doublet chemotherapy in post-TKI EGFR-mutant lung cancer, an endpoint that cannot be gamed, and became the first TROP2 ADC approved in lung cancer anywhere.²⁹ It has hit Phase 3 primary endpoints in first-line NSCLC on both sides of the PD-L1 biomarker divide, ahead of the Western competition on published data.²²²³

Behind it stands a global partner running seventeen Phase 3 trials at its own expense, which means Kelun-Biotech holds an option on Western commercialization economics without bearing Western development costs.⁵ The safety profile reported to date — no interstitial lung disease, limited gastrointestinal toxicity — is a genuine potential differentiator in a class where tolerability determines how long patients stay on therapy and therefore how much drug gets sold.⁴ And the shift to product-driven revenue is happening fast enough to be visible in a single half-year.³¹

The structural argument sitting underneath all of this is that global pharmaceutical companies face a decade of patent expiries and cannot fill the gap from their own laboratories at acceptable cost, while Chinese originators can develop assets to proof-of-concept at a fraction of Western expense. Kelun-Biotech was early to that trade and is among the small number of Chinese biotechs that can both originate and commercialize.

The case against

Now the counterevidence, and it is not manufactured.

The headline that made this company famous overstates its economics by an order of magnitude that is difficult to overstate. Of seven preclinical candidates in the $9.3 billion December 2022 agreement, several were returned or declined within two years, and the incremental cash Merck has paid to exercise an option since then was $37.5 million.¹⁷¹⁸ Merck's own portfolio decisions — made after it bought a $22 billion competing ADC portfolio — are the best available evidence on how a fully informed party values Kelun-Biotech's early-stage pipeline, and that evidence says: selectively, and not at the headline.

The profitability inflection leans on a one-off. A RMB700 million legal settlement received in June 2026 exceeded the RMB388 million reported net profit for the half.³²³¹ Underlying operations remained loss-making.

The equity issuance record is at odds with the self-image of a disciplined, cash-rich company: three discounted placements since a 2023 IPO, the most recent at an 8.5% discount for HK$2.72 billion net, while RMB1.5 billion of disclosed cash sat in bank wealth-management products.³⁷³⁸ Reported losses widened in 2025 rather than narrowing.²⁸

The competitive thesis rests on cross-trial comparison rather than proof. No head-to-head study has compared sac-TMT with Trodelvy or Datroway, and the incumbent's actual commercial performance — approximately $1.4 billion in 2025 sales growing 6% — sets a sobering ceiling on what a well-executed TROP2 franchise has been worth in practice.¹⁹ Meanwhile the Chinese reimbursement system is designed to convert clinical success into volume rather than into margin.

And the company remains majority-controlled by a generics parent, with continuing related-party arrangements and a minority float that has no capacity to influence them.

Weighing it

Placing these side by side is not analysis, so here is the verdict, claim by claim.

The "platform validated by Merck" claim is rejected in its strong form and survives in a narrow one. The correct statement is that Merck validated specific molecules, principally sac-TMT and SKB571, and discarded the rest when its strategy changed. Investors should price the retained assets, not the portfolio.

The "differentiated chemistry" claim is intact but unproven. The linker and payload are demonstrably different; the DAR is demonstrably higher; the safety profile reported to date is demonstrably favorable on ILD. None of that has been tested against a competitor in a randomized trial, and the reported safety advantage is drawn from populations that have not yet been observed at post-approval scale or duration.

The "commercial execution" claim is intact and improving. Management set specific headcount, coverage, and revenue targets on the 2025 annual results call and met or tracked them by the 2026 interim results.³³³¹ Two data points is a thin base, but it is the right kind of evidence.

The "profitability inflection" claim is not yet supported. One half-year of profit made possible by a settlement is not an inflection. It becomes one when product sales alone cover the cost base.

The "capital discipline" claim is unsupported on current evidence. Three discounted placements against a large cash balance, with generic use-of-proceeds language and no detailed public explanation, is a pattern that requires either a better explanation from management or a lower assumption about self-funding capacity.

What emerges is a company whose achievements are real and whose most famous number is not. The thing that would most efficiently resolve the remaining ambiguity is boring and specific: several consecutive periods in which product sales alone, unaided by milestones or settlements, cover the operating cost base.

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XII. Risk Radar

Every biotech carries the same generic risks — trials fail, regulators say no, competitors win. The risks worth an investor's attention here are the ones specific to how this particular company is built.

Partner concentration. Merck is simultaneously the dominant licensing counterparty, the funder of the global development program for the lead asset, and the largest external shareholder.⁸⁵ There is no comparable second relationship of that scale; the Windward Bio transaction is real but an order of magnitude smaller.³⁹ The mechanism of harm is not that Merck behaves badly — it is that Merck's oncology strategy is set in Rahway for Merck's reasons, and Kelun-Biotech's near-term value moves with decisions it does not participate in. This is not hypothetical: it is precisely what happened in October 2023 and again in August 2024, when Merck's acquisition of a competing ADC portfolio was followed by candidates being handed back.¹⁷¹⁸ The concentration risk has already fired once.

Earnings quality and revenue lumpiness. Development and regulatory milestones from a partner arrive on contractual triggers, not on operating rhythm — roughly $90 million recognized in a single half of 2024, a legal settlement of RMB700 million in a single month of 2026.³² The chief financial officer made the accounting point explicitly on the 2025 annual results call: collaboration revenue recognition follows accounting principles and is not one-for-one with cash milestones received.³³ The practical consequence is that any single period's revenue or profit figure for this company is uninterpretable unless product sales are separated from everything else. Investors should insist on that split in every reference.

Class-wide safety risk. Interstitial lung disease is the shadow hanging over the entire ADC class, most visibly in the deruxtecan-based conjugates. Sac-TMT's reported profile has been favorable on this specific risk.⁴ But the population that generates safety signals is not the trial population — it is the larger, older, sicker, less closely monitored post-approval population, observed over years rather than months. A clean signal in registrational trials is encouraging and is not the same as a clean drug. This is the highest-impact single-event risk in the story, because an ILD signal at scale would simultaneously remove the differentiation claim and constrain the commercial opportunity.

Intellectual property, in an unusual direction. Reviewing the public record for this piece, no TROP2-related patent litigation brought by Gilead, Immunomedics, or any other originator against Kelun-Biotech was identified — a bounded negative finding for the period reviewed, not a permanent assurance, and one that says nothing about claims that may be filed as the molecule expands into Western markets. What the record does contain is litigation running the other way: Kelun-Biotech pursued claims of trade-secret misappropriation and other civil litigation against 宜联生物 MediLink Therapeutics and associated individuals, settling on December 16, 2025 in an arrangement under which MediLink shares a portion of income and profits from a defined set of pipeline products with Kelun-Biotech, both from out-licensing transactions already completed and from future sales.⁴⁰³²

That settlement is more analytically interesting than it first appears, for three reasons. It converted a legal claim into a continuing economic interest in another company's pipeline — an unusual, quasi-royalty asset that will produce lumpy income for years. It was the proximate cause of the first reported profit. And it tells you something about the nature of the moat: in a field where composition-of-matter patents are the classical defense, this company's most consequential IP action was a trade-secret claim, which is the remedy you reach for when the thing being protected is know-how held by people rather than claims in a granted patent. Know-how walks out of buildings. That is a structural feature of ADC platform companies generally, and it cuts against treating OptiDC as a durable cornered resource.

Geopolitics. The US BIOSECURE Act was signed into law on December 18, 2025 as part of the FY2026 National Defense Authorization Act.⁴¹ Its architecture matters more than its headline: it restricts federal agencies, contractors, and grant recipients from procuring biotechnology equipment or services from designated "biotechnology companies of concern," with the designation list to be published within a year of enactment through a Department of Defense and OMB process.⁴¹ Notably, the enacted version does not itself name specific companies, unlike earlier drafts that had listed genomics and contract-manufacturing firms.⁴¹ The statute targets services and equipment procurement — the CDMO and genomics model — not asset-licensing biotechs, and Kelun-Biotech's business with Merck is a license of intellectual property, not a service contract with the US government.

The best available evidence that the sector has absorbed this is the deal data itself: Chinese cross-border out-licensing reached a record of roughly $136 billion in 2025, the year the law passed, roughly triple the prior year.²⁶ That is a strong empirical counterweight to the "geopolitics kills these deals" narrative. The residual, real risk is subtler — heightened diligence burdens, intellectual-property scrutiny, and political sensitivity around US patients being treated with China-originated medicines, all of which raise the friction and cost of every transaction without prohibiting any of them.⁴² Treat it as a rising cost of doing business and a tail risk on policy escalation, not as a present threat to this company's contracts.

Dilution. Covered above, and it belongs on this list precisely because it is the risk most likely to be dismissed as housekeeping. Three discounted placements in three years is a pattern with a straightforward test attached: if the company issues again without a specific, articulated need, the "opportunistic financing" explanation gets harder to sustain.³⁵³⁶³⁷

Reimbursement price pressure. The mechanism that makes Chinese oncology volumes explode is the same mechanism that caps their value. NRDL inclusion from January 1, 2026 delivers access at a negotiated price, renegotiated periodically, in a system explicitly designed to extract price as volume grows.²⁸ A franchise can double in units and grow far less in revenue. This is the most predictable of the risks listed here and the one most often left out of enthusiastic models.

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XIII. Playbook: Business & Investing Lessons

Patient capital from a boring business can fund a real platform — but count the years honestly. The generics-and-infusions cash flow that funded Kelun-Biotech's first six years produced no external validation until 2022 and no product revenue until 2024. Eight years elapsed between founding the research arm and selling the first vial. Very few public-market structures tolerate that, which is exactly why the bet was made inside a private subsidiary of a profitable industrial parent rather than in a listed vehicle. The transferable lesson is structural: the ownership form determines how long a bet can stay unvalidated, and therefore which bets can be made at all.

Biobucks are options, not contracts, and the market prices them wrong in both directions. The discipline is to model the realistically exercised subset — here, a minority of the original seven candidates — and to treat the up-front payment as the only number both parties agreed was worth actual money. The corollary is subtler: a low up-front payment relative to a high ceiling is itself information about how confident the buyer is.

A partner who is also a shareholder is aligned, not omniscient. Merck's equity stake genuinely aligns it with the company's success. It did not stop Merck from handing back assets when its own strategy shifted. Alignment tells you a counterparty will not act against you; it does not tell you the science works. Independent evidence — approvals, survival data, product sales — is what tells you that.

A first approval is a beachhead, not a moat. Being the first TROP2 ADC approved in lung cancer is a genuine achievement that confers real advantages in prescriber familiarity and reimbursement sequencing. It confers no protection against a competitor arriving with better data. The moat question is always downstream: does the chemistry differentiation show up in comparative outcomes, in tolerability that keeps patients on drug longer, and in price realization? Approval order answers none of those.

Watch what the accounts are made of, not what they total. A company can report record revenue while its recurring business shrinks, and report its first profit while its operations lose money. Both happened here, in the same year, for legitimate accounting reasons. The composition of revenue is the analysis; the total is the headline.

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XIV. Epilogue & What to Watch

Three things matter more than everything else, and all three are observable.

First, product sales excluding milestones and one-off items. This is the single most important number in the company. It strips out the settlement, the licensing lumpiness, and the accounting timing, and answers the only question that determines whether Kelun-Biotech is a durable pharmaceutical business or a research organization with an unusually good year. Management has guided to full-year 2026 commercialization revenue at least doubling the 2025 level and to sustainable break-even in the 2026 to 2027 window.³¹ Those are checkable commitments with dates attached.

Second, first-line NSCLC combination outcomes — specifically overall survival, and specifically in the global program. Kelun-Biotech has reported progression-free survival wins in both PD-L1-positive and PD-L1-negative first-line settings.²²²³ PFS gets you to a conversation; OS gets you to a standard of care. The relevant readouts sit inside Merck's seventeen-trial global program, and they will be adjudicated against AstraZeneca and Daiichi Sankyo's competing first-line studies, whose data are expected after 2026.⁵²⁵ This is where the largest population in the class gets allocated.

Third, the shape of the Merck relationship. Additional option exercises, or a new platform-level agreement, would restore the broad version of the platform thesis. Continued quiet narrowing toward sac-TMT alone would confirm the narrow version. This is a binary that resolves through announcements, not estimates.

What would most damage the case from here: an interstitial lung disease or other safety signal emerging in post-approval sac-TMT use at scale; another Merck candidate returned without a replacement agreement; a fourth discounted equity placement with no specific articulated need; or a first-line combination readout that fails on overall survival while a competitor's succeeds.

What would most strengthen it: two or more consecutive reporting periods of profit generated by product sales alone; positive overall survival data from the global first-line combination program; an expanded Merck commitment; and evidence that the NRDL price concessions are being more than offset by volume, which is the specific test of whether a Chinese oncology franchise can be worth what its clinical data suggest.

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XV. Outro

Kelun-Biotech is two things at once, and the discomfort of holding both ideas is the point.

It is one of the clearest available proof points that Chinese biotechnology has become genuinely investable — a company that discovered its own molecules, took them through a regulator, demonstrated an overall survival benefit, built a national commercial organization, and did it all inside a decade, funded initially by the proceeds of selling saline bags to hospitals.

It is also a case study in why headline deal values require a skeptic's discount. The $9.3 billion number that made this company famous was never a forecast; it was a ceiling across seven shots on goal, most of which missed, and the partner who wrote it has since demonstrated exactly how conditional it always was.

The interesting thing about this story is that the second fact does not diminish the first. What Kelun-Biotech has actually built turns out to be more defensible than what it was celebrated for. The molecules that reached patients did more for the company than the ones that were licensed and returned. That is usually how it goes, and it is usually noticed much later than it should be.

Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd.

Table of Contents

Kelun-Biotech: How a Chinese IV-Drip Maker's Cast-Off Bet Became Merck's Most Expensive Shopping Trip

I. Introduction & Episode Roadmap

II. Origins: The Cash Cow That Funded the Moonshot

III. Building OptiDC: The Platform Bet

IV. The Merck Inflection: Three Deals in Eight Months

V. Going Public on the Halo

VI. Stress-Testing the Deal: What Happened to the Seven Candidates

VII. The Core Business: Industry Structure & the TROP2 Battlefield

Why the whole industry pivoted to ADCs

TROP2: the largest prize, and the most crowded arena

What the clinical evidence actually shows

The frontier: first-line lung cancer

The rest of the Chinese ADC field

Industry structure: why this is happening at all

Five Forces and 7 Powers, applied honestly

VIII. From Platform to Pharmacy: Approvals and the Profitability Inflection

IX. Money In, Money Out: Financials and Capital Allocation

X. Who's Running It Now

XI. Bull vs. Bear: Stress-Testing the Investment Case

The case for

The case against

Weighing it

XII. Risk Radar

XIII. Playbook: Business & Investing Lessons

XIV. Epilogue & What to Watch

XV. Outro

References