Merus has reported a 79% 12-month survival rate in cancer patients on its bispecific antibody, cementing William Blair analysts' belief the candidate has a “best-in-disease profile.”
The bispecific binds EGFR and LGR5 on cancer cells. EGFR is an established cancer drug target while LGR5 is a novel target. By hitting both receptors, Merus believes its bispecific petosemtamab can inhibit EGFR signaling, drive EGFR degradation via LGR5 and engage the immune system. The biotech shared data to support its case ahead of the American Society of Clinical Oncology (ASCO) annual meeting early next month.
Merus’ data set covers 45 patients with PD-L1-positive recurrent or metastatic head and neck squamous cell carcinoma. Participants in the phase 2 trial received petosemtamab and Merck & Co.’s blockbuster oncology drug Keytruda, which is approved in the setting, as a first-line treatment.
In the 43 evaluable patients, Merus reported a 63% response rate, including six complete responses. The overall response rate is in line with an earlier glance at the data that looked at 24 patients. There was one complete response in the earlier cut of the data.
Merus now has some survival data from the trial. Median progression-free survival was nine months. Overall survival at 12 months was 79%. The study was yet to reach the median duration of response and overall survival as of the data cutoff.
The study lacks a control arm, but cross-trial comparisons—which can be unreliable—cast petosemtamab in a good light. Keytruda had (PDF) a 19% response rate and 51% 12-month survival when given as a single agent in a registrational trial. Merus’ data stack up well against an EGFRxTGF-β bispecific in development at Bicara Therapeutics, which reported 12-month survival of 61% Thursday.
Merus CEO Bill Lundberg, M.D., spoke bullishly about the data on a conference call with investors. After reviewing the cancer literature, Lundberg argued the study’s 12-month survival rate is “unprecedented.” If Merus replicates the phase 2 results in phase 3, the addition of petosemtamab to Keytruda “is likely to be transformational in the front-line treatment of PD-L1-positive head and neck cancer,” the CEO said.
Lundberg is confident that Merus’ two phase 3 registration trials should be “substantially enrolled” by the end of the year. The use of the term “substantially enrolled,” which the FDA uses in relation to the criteria for accelerated approval, prompted an analyst question about whether Merus could file to bring the drug candidate to market before a pivotal trial reads out in 2026.
“We do believe that there's a real opportunity ... for there to be a potential accelerated approval based on an early endpoint such as ORR with confirmation coming from survival in the same setting,” Lundberg said. The FDA’s accelerated approval response rate criteria require two assessment cycles, the CEO said, and it wants to see evidence of durability and an early look at how overall survival is trending.
Shares in Merus jumped 13% in premarket trading Friday morning, rising to above $47 on a $2.8 billion market cap.