RAPT Therapeutics, Inc. announced safety and efficacy data from its ongoing Phase 2 trial of tivumecirnon in combination with the anti-PD-1 checkpoint inhibitor (CPI) pembrolizumab in the cohort of patients with advanced head and neck squamous cell carcinoma (HNSCC) whose disease progressed despite previous treatment with CPI therapy (CPI-experienced). The results were presented at the American Association for Cancer Research (AACR) Annual Meeting in San Diego, CA. The AACR poster highlighted data from the 32-patient CPI-experienced HNSCC cohort in the trial evaluating tivumecirnon, an oral small molecule CCR4 antagonist designed to block the migration of regulatory T cells, in combination with pembrolizumab.

Patients in this cohort had heavily pretreated disease, with 69% of patients having received three or more (up to six) prior lines of treatment. In the entire cohort, confirmed responses were observed in 5/32 patients (15.6%) regardless of PD-L1 or HPV status. In the 23 patients known to have PD-L1+ disease (CPS =1), an ORR of 17.4% (4/23) was observed, and in the 18 patients known to have HPV+ disease, an ORR of 22.2% (4/18) was observed.

These findings compare favorably to the expected ORR of anti-PD-1 monotherapy in patients with recurrent or metastatic HNSCC who have progressed on, or relapsed after, previous anti-PD-1 therapy, which is believed to be <5-10%. These data complement previously reported clinical data for tivumecirnon, which has now been dosed in more than 350 patients with various advanced cancers either as monotherapy or in combination with pembrolizumab. Findings to date have shown the combination treatment to be well tolerated with no signal of increased immune-related toxicity over that expected with pembrolizumab alone.