Magrolimab

Pheast Therapeutics may have learned the hard way about the risks of competitors getting a glimpse of your hard-earned discoveries, but the immuno-oncology startup is sticking to its transparent approach for now. The Redwood City, California-based biotech was set up in 2021 to take forward the work of its scientific founder Irv Weissman, M.D., conducted at the Stanford University Institute for Stem Cell Biology and Regenerative Medicine. Weissman’s findings, laid out in an influential paper published in Nature in 2019, drew attention to the CD24 protein’s “don’t eat me” signal as a promising target for cancer immunotherapy . That interest helped the company raise a $76 million series A in 2022, which the biotech used to advance an IgG4 anti-CD24 macrophage checkpoint inhibitor, dubbed PHST001, into clinical trials for advanced solid tumors. Pheast dosed its first patients in April 2025. But despite Weissman’s pioneering work, Chinese biotech Antengene had already beaten Pheast to the table to become the first company to take an anti-CD24 drug into human trials. Antengene’s candidate, dubbed ATG-031, entered the clinic in 2023. According to the federal trials database , that U.S. trial finished in June. Pheast’s experience has since been cited to Fierce by some biopharma observers as an example of why biotechs need to take a more secretive approach to their pipelines in such a competitive environment. But Pheast CEO Roy Maute, Ph.D., told Fierce that the company has no regrets about shouting about its research. “Some companies benefit from maximum secrecy,” Maute said in an interview. “We’ve honestly taken the opposite tact of saying, ‘We've got something completely new. We think we have a different way to approach this target than how others might think about it.’” Still, the CEO admitted that being beaten into human trials “wasn't a uniformly positive initial angle at that point in time of our clinical development.” “But, in the meantime, the world has turned, and now we've made exactly the progress that we’d hoped to make with our clinical program,” he added. That progress has led Pheast to kick off the phase 1b portion of its trial, assessing PHST001 in combination with chemotherapy. The company expects a readout on the study next year. “We're quite pleased with the speed at which we’re moving,” said Maute, a co-founder of the company who stepped up to the CEO role in 2024 after serving as chief scientific officer. “Our focus is on trying to deliver effective drugs for patients, and that presses us—like it does many other companies—to move as fast as we practically can,” he continued. “But one needs to do that with the right science.” “We knew when we were starting Pheast that CD24 was a bit of an unusual target that had some specific technical challenges, and we were confident that we needed to dig into the science and get it right the first time,” Maute added. The initial clinical results have been promising. In April, Pheast unwrapped a slice of phase 1a data at the American Association for Cancer Research Annual Meeting in San Diego. It showed that PHST001 was “generally well-tolerated across dose-escalation cohorts,” with “most” treatment-related adverse events limited to grade 1 or 2. While a subset of patients experienced transient neutrophil decrease, these cases were manageable and not associated with clinical complications, the company said at the time. In addition, Pheast was able to point to early signs of clinical activity, such as disease stabilization and tumor shrinkage. “That class of drug is one where there’s sort of a desperate interest from the side of clinicians, because they see it as addressing an obvious need in the landscape of many of the cancers that they treat,” Maute said. “But it’s one that’s seen some clinical stumbles in the past.” Those stumbles have centered around CD47, the first macrophage checkpoint to attract serious interest among biopharmas for its “don’t eat me” signal. However, safety concerns ended hopes for some high-profile anti-CD47 candidates like Gilead’s magrolimab . More recently, Pfizer scrapped work on two CD47 inhibitors from its $2.3 billion bet on Trillium Therapeutics, although the Big Pharma was keen to stress that the decision was not related to any safety issues. Set against this backdrop, it’s easier to understand why Pheast has been keen to keep investors updated on PHST001’s progress. “We felt like once we had achieved that understanding of our drug safety, it was worth talking about even if the study was still in progress,” Maute said. The biotech is continuing this approach of relative transparency with another candidate. At the Protein & Antibody Engineering Summit in Boston in May, Pheast presented preclinical data for PHST677, a bispecific antibody-drug conjugate (ADC) targeting both CDH1 and Nectin-4. At the time, Maute heralded the data as the first public disclosure of CDH1 as a novel immune-regulatory ADC target and pointed to PHST677 as evidence of how the company’s genomic screening platform can “unlock targets previously inaccessible to traditional ADC approaches.” The CEO told Fierce that the choice to continue sharing early data and new science is about balancing the “push-pull of making sure that people out there know what you're doing and you're getting them excited about its potential” against the desire to “keep the head start that you've established if you're doing something novel.” “We think about investor audiences, but we also think about the clinical community and the patient community and having people have some understanding of what we're doing,” he said. “Once those drugs arrive in the clinic, we’re able to build on a foundation of understanding of why this would be different and why it would be better than what’s out there,” the CEO added. “That involves some level of talking publicly about what your target is.” Even though Pheast has so far leaned into a more open approach to drug development and sharing data, that rule isn’t set in stone. Each new asset is a new conversation. “I wouldn’t say it’s something we've decided forever for the company,” Maute said. “We've asked ourselves amongst the team, the leadership and the board: ‘What is the right decision here?’”