The story of giants spending heavily on shopping has encountered a backlash in the ADC track.

In September, Pfizer transferred an under development ADC codenamed PF-08046031 to an unknown Pennsylvania biotech company, Medicus Pharma, for a down payment of only $12 million.

This money is insignificant compared to Pfizer's size, but it has caused significant ripples in the industry.

The predecessor of PF-08046031 was Seagen's SGN-CD228A. When Pfizer bought Seagen for $43 billion in 2023, this CD228 targeted ADC was still a highly anticipated asset. Three years later, it went from a strategic asset to a "abandoned son" waiting to be sold, and Pfizer defined this termination as a "strategic evaluation".

In fact, the preclinical data of this product is not bad: at a dose of 6mg/kg, it reduced tumors induced by two melanoma cell lines by 87% and 90%, respectively. Pfizer launched Phase I trials in May 2025, covering melanoma, lung cancer, head and neck cancer, and esophageal cancer, but abruptly ended in less than a year.

The resource allocation of MNCs follows the logic of "opportunity cost" rather than "absolute value". An early project, even if promising, will lose in internal competition with more mature assets if it fails to enter critical trials in the short term.

Combined with the financial amortization pressure brought about by the $43 billion acquisition, investors' expectations for return cycles, and the shift in strategic focus in organizational integration, PF-08046031 ultimately slid from "strategic assets" to "strategic redundancy".

But Pfizer has not completely let go - patent ownership, potential milestone payments of over $1 billion, and the right to review development plans have all been written into the agreement.

So, are the "abandoned children" of large pharmaceutical companies failed products that have been scientifically rejected, or are they "orphans" sacrificed by strategic priorities? Why should a small company with a market value less than a fraction of Pfizer's R&D budget believe that it can catch this opportunity?

01. A proven but not exhaustive target

If the scientific logic of PF-08046031 itself is untenable, then its story of flowing from Pfizer to Medicus is just a risk transfer. But in fact, the scientific foundation of CD228 as a target is much more solid than implied by the label 'abandoned by major pharmaceutical companies'.

Melanin transferrin was initially discovered in melanoma and has long been regarded as one of the hallmark antigens of melanoma. Subsequent studies revealed that CD228 is expressed in a variety of solid tumors, including squamous non-small cell lung cancer, triple negative breast cancer, colorectal cancer, and pancreatic cancer, while its expression in normal tissues is relatively limited.

This expression profile constitutes the classic ideal conditions for ADC development: high expression in tumors to drive targeted delivery, and low expression in normal tissues to limit targeted toxicity.

More importantly, CD228, as a cell surface protein, has efficient antibody mediated internalization ability. Published preclinical studies have shown that anti-CD228 ADC constructs based on hL49 antibodies can be efficiently internalized in various tumor cell types, and their cytotoxic activity is significantly correlated with CD228 expression levels, internalization efficiency, and inherent sensitivity of tumor cells to MMAE payloads.

This means that CD228 is not only an 'existing target', but also a 'deliverable target' that can truly deliver the payload into the cell after antibody binding.

PF-08046031 adopts vedotin platform technology, humanized IgG1 monoclonal antibody hL49, coupled to MMAE through protease cleavable valine citrulline linker, with an average DAR of 4. This is consistent with the technical pathway validated by Seagen/Pfizer in marketed drugs such as Adcetris and Padcev.

Although PF-08046031 itself has not been clinically validated, every component in its "toolbox" - antibody backbone, linker chemistry, and payload - has undergone clinical testing in other ADC products, significantly reducing the "platform risk" of the asset.

As of now, there are no approved therapies targeting CD228 worldwide. Pharma ONE data shows that BA1302 of BoanBio is the only CD228 targeted ADC drug in the world that has entered the clinical stage. It has completed the phase Ia dose increase study in China, and is about to enter the phase Ib extended test. It has been awarded two orphan drug qualifications by FDA for squamous non-small cell lung cancer and pancreatic cancer; EM-1033 from Anmai Biotechnology is in the preclinical stage, and all other ongoing pipelines have been terminated.

02. Building a pipeline "story"

Medicus Pharma is not a traditional ADC company. Its core asset was originally SkinJect, a non-invasive delivery system based on soluble microneedle arrays for the treatment of basal cell carcinoma; And Teverelix, a next-generation GnRH antagonist used for indications related to prostate cancer.

From this perspective, introducing PF-08046031 is a seemingly abrupt strategic choice.

But upon closer inspection of Medicus' situation, the underlying logic of this transaction becomes clear. As a multi strategy biotech company, Medicus' core demand is to build a compelling pipeline story to support its ongoing financing and valuation growth.

The Phase II data of SkinJect showed that the clinical clearance rate of the 200 µ g group was 73% after 57 days, but the histological clearance rate was only 40%. In addition, the active placebo group also had a clinical response rate of 38%, suggesting that microneedle physical stimulation may contribute to some of the efficacy, and the incremental value of drug delivery still needs to be more rigorously validated. Although Teverelix has been approved by the FDA to initiate Phase IIb research, it is still far from key trials and commercialization.

Under this pipeline structure, PF-08046031 provides Medicus with a ticket to enter one of the hottest sectors in the biotechnology industry, the ADC field. Some viewpoints point out that the biggest innovation in the future lies in the payload side, where payload design, antibody engineering, and coupling technology are key competitive axes shaping the next generation of ADCs.

The vedotin platform technology carried by PF-08046031, although not considered the "next generation", is a validated "this generation", and the differentiated positioning of CD228 targets provides Medicus with a relatively low competitive entry angle.

What is more worth pondering is the transaction structure itself. Medicus made a down payment of only $12 million, with an additional $15 million paid on the first anniversary, while Pfizer provided $2 million in development funding in return. This means that Medicus' initial net cash expenditure was only $10 million, yet it acquired an ADC asset with global rights.

If subsequent development fails, Medicus' losses will be relatively limited; If successful, Pfizer's milestone payment of over $1 billion and low double-digit tiered licensing fees would only be seen as "icing on the cake" from the perspective of major pharmaceutical companies. This unequal risk return structure is exactly the leverage that small biotech companies are worth fighting for when negotiating with large pharmaceutical companies.

But it must be pointed out that Pfizer has not truly let go. According to SEC documents, Pfizer reserves the right to review and comment on development plans, to meet with the Medicus team to discuss asset related matters, and to request regular progress reports. More importantly, Pfizer has the right to choose to fund all or part of future development work after the initiation of critical trials.

It can be said that this is a double-edged sword: on the one hand, Pfizer's continued involvement provides potential resources and endorsement for Medicus; On the other hand, if Pfizer chooses not to provide funding, this' silence 'itself may be interpreted by the market as a negative signal.

03. "Abandoned Child" Economics

The transaction between Medicus and Pfizer is not an isolated case. In the entire biopharmaceutical industry, assets abandoned by large pharmaceutical companies due to strategic adjustments are becoming an important target pool for small biotech and venture capital firms.

In 2017, Pfizer spun off a group of rare disease drugs to the newly established SpringWorks, including nirogacetat, which later became the first treatment for hard fibroids. SpringWorks focused on promoting it and was ultimately approved in 2023. Similarly, in 2018, Pfizer partnered with Bain Capital to establish Cerevel, injecting multiple CNS candidate drugs. After independent listing, it was acquired by AbbVie for $8.7 billion in 2023.

The commonality of these cases is that they are seen as non strategic priority assets by large pharmaceutical companies, regaining attention on resource focused small platforms, with venture capital providing start-up capital and management teams, and profiting through equity appreciation.

The underlying reason is that large pharmaceutical companies and small biotech companies have different definitions of 'failure'. For a large company like Pfizer, an early-stage ADC project, even if scientifically justifiable, may not be worth investing in if it cannot generate peak sales potential of billions of dollars within 3-5 years.

The "threshold return rate" of large pharmaceutical companies naturally leans towards later stage assets and listed products, as cash flow predictability is higher and the cost of communication with Wall Street is lower. Small companies, on the other hand, value the "selectivity" of early assets, with limited down payments and controllable downside risks, and only need to generate positive signals to support the next round of financing or higher value cooperation. But the premise of arbitrage is that small biotech companies must have the ability and resources to truly advance assets, including clinical design, manufacturing, regulatory communication, and fundraising.

When the Phase I trial of PF-08046031 was terminated by Pfizer, insufficient clinical data was generated to determine its true safety and efficacy signals. Medicus needs to redesign its clinical development plan after taking over, and in this process, the "half data" left by Pfizer's previously launched trials may be both assets and burdens.

Manufacturing and supply chain are a real challenge. The complexity of ADC far exceeds that of small molecule drugs and even ordinary biologics, involving multiple links such as antibody production, linker synthesis, coupling process, DAR control, etc. Medicus itself does not have ADC manufacturing capabilities and must integrate external CDMO resources within the protocol framework and meet Pfizer's review requirements for development plans and budgets.

Medicus' own financial situation and financing capabilities will also be put to the test. Although the down payment is not high, the clinical development cost of ADC can easily reach tens of millions or even billions of dollars. Medicus is currently simultaneously advancing the follow-up development of SkinJect, Teverelix, and PF-08046031. The parallel development of these three fronts means extremely high execution complexity and funding requirements for a small biotech with limited resources.

The risks inherent in science have never disappeared. Although the target logic of CD228 has been supported in preclinical data, there have been many seemingly reasonable targets that have failed on the path of clinical validation. There are differences in linker chemistry between SGN-CD228A and PF-08046031 mentioned in published studies, which are related but different. This means that preclinical data cannot be directly extrapolated.

In the innovation ecosystem of biomedicine, 'abandoned child' is not an absolute label, but a strategic choice made by specific enterprises under specific constraints. PF-08046031, which was abandoned by Pfizer today, may become the cornerstone of Medicus tomorrow; If the promotion is not effective, it may also change hands again and enter a new cycle of "abandoned children" and "opportunities".

Reference article:
1. The drug that Pfizer once abandoned is now on a comeback!; Sina Finance
2. Pfizer CD228 ADC drug PF-08046031 has been transferred and restarted, and the 43 billion Seagen acquisition pipeline is undergoing asset adjustment; Moentropy Medicine
3 Medicus Pharma Licenses Pfizer's Discontinued CD228-Targeted ADC in Deal Worth Over $1 Billion； biopharma
4. Over 1 billion US dollars! Pfizer transfers an ADC; Medical Magic Cube Info