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EP4, a prostaglandin E2 receptor, has shown an immunosuppressive activity on cancer cells. This first‐in‐human study evaluated ONO‐4578, a highly selective EP4 antagonist, as monotherapy and in combination with nivolumab in patients with advanced or metastatic solid tumors. A daily dose ranging from 30 mg to 100 mg of ONO‐4578 monotherapy and that ranging from 2 mg to 60 mg of ONO‐4578 with biweekly nivolumab 240 mg were administered. A total of 31 patients were enrolled, 10 receiving monotherapy and 21 receiving combination therapy. Overall, 26 patients experienced treatment‐related adverse events. Dose‐limiting toxicities were observed in three patients; one of six patients receiving 100 mg monotherapy developed grade 3 duodenal ulcer and two of six patients receiving 60 mg combination therapy developed either grade 3 erythema multiforme or grade 3 increased amylase and grade 4 increased lipase. One patient with small‐cell lung cancer who received 40 mg combination therapy had a partial response, and three patients with monotherapy and six patients with combination therapy had stable disease. Pharmacodynamics analyses showed that ONO‐4578 had EP4 antagonistic activity at doses as low as 2 mg. In conclusion, the maximum tolerated dose of ONO‐4578 alone or in combination with nivolumab was not reached. ONO‐4578 was well tolerated at the tested doses and showed signs of antitumor activity. Considering safety, efficacy, and pharmacokinetics/pharmacodynamics results, ONO‐4578 40 mg daily with nivolumab 240 mg biweekly was selected as the recommended dose for future clinical trials. (Registration: JapicCTI‐173,496 and NCT03155061). [ABSTRACT FROM AUTHOR]

PIK3CA mutations are common activating mutations associated with breast cancer (occurring in 20–30% of all cases) and are potent predictive markers for responses to PI3K inhibitors. Thus, it is important to develop sensitive methods to detect these mutations. We established a novel detection method using a quenching probe (QP) system to identify PIK3CA mutations, using DNA from 309 breast cancer tissues. In a developmental cohort, we determined the optimal detection threshold of the QP system with human tumor DNA from 119 freshly frozen tumor samples. We found a 96% concordance rate with the QP system between DNA from 26 matching fresh‐frozen specimens and formalin‐fixed paraffin‐embedded (FFPE) specimens from the same patients, and known PIK3CA mutation status in the developmental cohort. In a validation cohort, we evaluated whether the threshold for judging mutations using the QP system with frozen specimen‐derived DNA was applicable with FFPE‐derived DNA. In the validation cohort, 30 DNA samples from 190 FFPE‐derived DNA samples with known PIK3CA mutation status were analyzed by direct sequencing (DS) and droplet digital PCR, in a blinded manner. The sensitivity and specificity of the droplet digital PCR results were 100% and 100% (QP system), and 60% and 100% (DS), respectively. We also analyzed the relationship between clinical outcomes and the PIK3CA mutational status of 309 breast cancer samples, including the developmental cohort and validation cohort samples. Multivariate analysis suggested that PIK3CA mutations, especially H1047R, were prognostic factors of relapse‐free survival. Our novel detection system could be more useful than DS for detecting clinical PIK3CA mutations. [ABSTRACT FROM AUTHOR]

EP4, a prostaglandin E 2 receptor, has shown an immunosuppressive activity on cancer cells. This first-in-human study evaluated ONO-4578, a highly selective EP4 antagonist, as monotherapy and in combination with nivolumab in patients with advanced or metastatic solid tumors. A daily dose ranging from 30 mg to 100 mg of ONO-4578 monotherapy and that ranging from 2 mg to 60 mg of ONO-4578 with biweekly nivolumab 240 mg were administered. A total of 31 patients were enrolled, 10 receiving monotherapy and 21 receiving combination therapy. Overall, 26 patients experienced treatment-related adverse events. Dose-limiting toxicities were observed in three patients; one of six patients receiving 100 mg monotherapy developed grade 3 duodenal ulcer and two of six patients receiving 60 mg combination therapy developed either grade 3 erythema multiforme or grade 3 increased amylase and grade 4 increased lipase. One patient with small-cell lung cancer who received 40 mg combination therapy had a partial response, and three patients with monotherapy and six patients with combination therapy had stable disease. Pharmacodynamics analyses showed that ONO-4578 had EP4 antagonistic activity at doses as low as 2 mg. In conclusion, the maximum tolerated dose of ONO-4578 alone or in combination with nivolumab was not reached. ONO-4578 was well tolerated at the tested doses and showed signs of antitumor activity. Considering safety, efficacy, and pharmacokinetics/pharmacodynamics results, ONO-4578 40 mg daily with nivolumab 240 mg biweekly was selected as the recommended dose for future clinical trials. (Registration: JapicCTI-173,496 and NCT03155061)., (© 2022 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)