Frontline Petosemtamab/Pembrolizumab Shows Early Efficacy in HNSCC

Cesar Augusto Perez, MD, hematologist and medical oncologist at Florida Cancer Specialists & Research Institute’s Lake Nona Cancer Center & Drug Development Unit, discusses the efficacy data reported in a phase 2 study (NCT03526835) of petosemtamab (MCLA-158) with pembrolizumab (Keytruda) for the first-line treatment of patients with recurrent/metastatic head and neck squamous cell carcinoma.

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0:09 | In terms of the efficacy, 67% of the patients developed a response, so there was a response rate of 67%. In total, there were 24 patients that had evaluable disease by RECIST1.1, there was 1 patient with a complete response, and 12 patients with a partial response, and there were also 3 patients with an unconfirmed partial response. There were patients with responses with HPV-negative and HPV-positive disease, and they also were divided among the CPS score. There were 10 patients with CPS between 1-19, and 14 patients with CPS of 20 [or higher]. And there were responses in both subsets. In CPS, 1-19, 60% of patients responded and patients with CPS more than 20, there was a 71% response rate, which is obviously very encouraging.

1:21 | In terms of the duration of response, most of the patients were still in response at the data cutoff. I think 1 of the things that I learned from these molecules that is very interesting is that you can see responses pretty early, which is something that we are not used to seeing in checkpoint inhibitors. Usually we have to wait a little bit longer. But for unknown reasons, the activity of this antibody can be seen pretty early on during the treatment course, which is very important for patients who are symptomatic, and that is very important, because some patients have a life-threatening disease in the immediate term, so we try not to lose patients, and the good thing military about this antibody is that we can see activity early on. And as a single-agent, we saw the same thing as in the combination arm.