Merus released additional head and neck cancer data from a Phase 2 study on Tuesday after publishing an ASCO abstract last week and outlined plans for a pivotal trial in the first-line setting.
The company reported data from 24 patients treated in the first-line setting of recurrent/metastatic head and neck squamous cell carcinoma that were eligible for evaluation. Petosemtamab, when added to Keytruda, induced a 67% overall response rate, including one complete response and 15 partial responses (12 confirmed).
A Phase 3 trial in that setting, likely comparing petosemtamab/Keytruda to Keytruda, is expected to start by the end of the year, Merus CEO Bill Lundberg told Endpoints News. After speaking with the FDA, he expects the study to serve as both the basis for an accelerated approval with ORR and include a confirmatory aspect to convert it to full approval with overall survival.
“From the FDA’s standpoint, they’ll get the receipts,” Lundberg said. “They won’t have to wait around for some sponsor to run another study. They’ll know the survival from that trial.”
There’s no timing yet on when the study will be fully enrolled, Lundberg added, but he pointed to a Merck trial in the same setting, KEYNOTE-048, that finished recruiting patients in under two years.
As the program approaches a potential approval, Merus — which has developed petosemtamab fully in-house — is likely to face questions about whether it can bring it past the finish line on its own, or whether it will need to engage in a partnership or acquisition.
Lundberg demurred on that topic in a Monday interview, instead generally emphasizing the opportunity in head and neck cancer and touting other programs in the company’s pipeline.
“We have the ambition to bring this drug forward to patients,” Lundberg said.
Merus’ results come a few days after it published an abstract at ASCO with data from only 10 patients, showing one complete response and five partial responses. The release sent Merus shares $MRUS up 36% on Friday.
Tuesday’s data also give Merus the confidence to run a first-line trial as an “all-comers” study, Lundberg said, enrolling patients regardless of PD-L1 expression level and whether or not their cancers were associated with HPV. Though the HPV-positive group only consisted of four patients, three saw their tumors respond to the therapy.
A total of 45 patients had been treated as of the March 6 data cutoff. Median follow-up time for the patients was 3.6 months.
During Tuesday’s investor call, Lundberg said researchers saw “quite a range of responses” in duration of treatment in spite of the relatively short follow-up time.
Merus’ ASCO presentation is scheduled for next Tuesday, when investors expect the company to provide swimmer plots showing how each patient responded to treatment in granular detail.
There were no life-threatening or fatal (grade 4 or grade 5) side effects, Merus reported. One patient discontinued treatment due to toxicity after their first cycle of treatment and was not included in the efficacy analysis.
Additionally, 38% of the full 45-patient group reported an infusion-related reaction of any severity. Of those, 7% reached grade 3 and none experienced grade 4 or grade 5. Most occurred during the first cycle of treatment and resolved afterward.
The company had previously announced a Phase 3 study for second-line treatment, expected to begin in mid-2024. It will follow a similar trial design as the first-line trial, Lundberg said.
Editor’s note: This article has been updated with information from Merus’ investor call.