Five Prime Therapeutics Inc. said it's licensing a family of monoclonal antibodies (Mabs) to Seattle Genetics Inc. for inclusion in new early stage cancer-killing antibody-drug conjugate (ADC) candidates, all directed to a single target. The deal holds $5 million up front for Five Prime, plus up to $525 million in milestone payments for the first two candidates. South San Francisco-based Five Prime's shares (NASDAQ:FPRX) rose about 18% on the deal, which interim CEO William Ringo said allows the firm "to realize value from our preclinical pipeline while prioritizing our clinical investments based on upcoming data readouts."
Under terms of the deal, Seagen gets exclusive global rights to the licensed MAbs and will be responsible for all R&D, manufacturing and commercialization of an ADCs based on them. Milestone payments are tied to development progress, regulatory and commercial achievements. Cumulative milestones could reach up to $295 million for the first ADC product developed, while additional tiered mid-single-digit royalties would be due on net product sales.
Seattle Genetics President and CEO Clay Siegall told BioWorld that the deal is part of his company's normal course of evaluating new early stage antibodies, targets and technologies. The company will be evaluating the MAbs in preclinical research along with many other interesting antibodies and targets, he said. The company has four INDs planned for filing this year and another four in 2021.
Regardless of its long-term outcome, though, the deal was good for Five Prime, providing a contrast to the failure of another of its antibodies, cabiralizumab. That asset, the subject of a 2015 collaboration with Bristol-Myers Squibb Co. that brought Five Prime $350 million up front, failed to provide a meaningful benefit for pancreatic cancer patients in combination with BMS's Opdivo (nivolumab). News of the phase II outcome left BMS with no near-term plans for additional sponsored development of cabiralizumab, Five Prime said Feb. 18.
Though neither Five Prime nor Seagen revealed the target of the licensed MAbs in the Feb. 19 deal, SVB Leerink analyst Jonathan Chang speculated that one potential target could be B7-H4, which Five Prime has previously described as an interesting target for an ADC, he said. "Management has consistently highlighted the ADC potential of B7-H4 in our past conversations with the team, noting the expression profile, lack of off-target toxicity, and other biologic factors make it an interesting target.," he said.
At the American Society of Clinical Oncology meeting in Chicago last year, researchers from Five Prime and affiliated organizations presented results from a first-in-human phase Ia/b study of the B7-H4 antibody FPA-150, according to BioWorld Science. And the candidate is currently under study as a monotherapy in a phase Ia/Ib trial in patients with advanced solid tumors. The same target is being pursued by Cambridge, Mass.-based Mersana Therapeutics Inc., which in January said it’s advancing a first-in-class ADC candidate targeting B7-H4, an antigen with a unique expression profile in the tumor and its microenvironment.
Five Prime, which seems likely to discuss the new licensing deal at least a little bit more during its Feb. 27 fourth-quarter earnings call, did not return a request for further comment on the Seagen deal Wednesday. However, comments by its chief medical officer, Helen Collins, at the recent J.P. Morgan Healthcare Conference in San Francisco seemed to echo Ringo's statement Wednesday about "prioritizing our clinical investments based on upcoming data readout."
In January, Collins said Five Prime's main focus in 2020 would be on advancing its clinical programs. One such candidate, the FGFR2b inhibitor bemarituzumab, is now in phase III for gastric and gastroesophageal junction cancer. With the help of partner Zai Lab Co. Ltd., it enrolled the trial so rapidly that further enrollment was paused until a futility analysis could be completed around midyear, she said. (What impact COVID-19 might have on that expectation, if any, wasn't immediately clear.)
Initial FPA-150 monotherapy and combination data, covering investigations in breast, bladder and gynecologic cancers, is also anticipated by midyear, followed by preliminary safety data on FPT-155, a soluble CD80 fusion protein, the company said in a recent presentation, posted on its website.
Shares of Five Prime closed Feb. 19 at $5.23, up 81 cents. Shares of Seagen (NASDAQ:SGEN) closed at $119.89, down 8 cents.