About a month after Pfizer CEO Albert Bourla, Ph.D., told investors that the Big Pharma’s pipeline pruning was mostly done, the company has trimmed another branch. Pfizer has scrapped a phase 1 antibody-drug conjugate that was being tested in solid tumors, a company spokesperson confirmed to Fierce Biotech.
The decision to remove PF-08046031 was made for “business reasons,” the spokesperson explained, and “was not related to any safety concerns or requests from regulatory authorities.”
PF-08046031 was once upon a time known as SGN-CD228A, and sailed over to Pfizer after the pharma’s titanic $43 billion buy of Seagen in 2023. The ADC targets CD228, which is another name for the iron-binding cell-surface protein melanotransferrin. CD228 has long been known to be abundant on melanoma cells, and Pfizer has since discovered that it is present on other types of solid tumors, too.
There are currently no approved drugs that target CD228. Pfizer’s now-terminated phase 1 trial of PF-08046031 kicked off in May 2025 and was primarily focused on advanced melanoma, but was exploring lung, head-and-neck and esophageal tumors.
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Since Seagen joined the Pfizer family, the biotech’s former assets have been steadily whittled away. Two of Seagen’s cancer candidates were dropped by Pfizer last November as part of a broader group of 11 total culls. That included a Seagen bispecific antibody that targeted CD228 and 4-1BB (also called CD137).
Just last month, Pfizer followed up by discontinuing six more pipeline programs, including a bladder cancer ADC candidate from Seagen called disitamab vedotin.
When announcing the terminated programs in a February call with investors, Pfizer’s Chief Financial Officer, David Denton, assured listeners that “the Seagen portfolio is progressing ahead of our expectations.”
CEO Bourla added that the New York drug giant had “done most of our pruning of our pipeline right now.” At the time, the now-canned PF-08046031 was still listed as an active program in Pfizer’s pipeline (PDF).
