Merck KGA’s Bavencio (avelumab) Phase Transition Success Rate (PTSR) in choriocarcinoma or gestational trophoblastic neoplasias (GTN) reached 67% after an investigator-initiated Phase II study in that indication was completed, as of 23 June.

The 24-patient Phase II trial (NCT03135769) was being conducted at Hospices Civils de Lyon, in patients with chemotherapy-resistant GTN. The condition is characterised by the persistence of elevated hCG titers after complete evacuation of an abnormal mass, consisting of trophoblasts, observed in pregnancy. Consequently, the trial’s success is being measured by the rate of patients with successful normalisation of hCG assays, its primary endpoint. The trial’s status as per its record was updated on 22 June, which pushed the PTSR score by nine points.

Previously, an update from this study with 15 patients was presented at the American Society of Clinical Oncology Annual Meeting in 2020. Among the treated patients, eight achieved successful hCG normalisations either during the treatment or after it was discontinued (abstract number LBA6008). One patient had a subsequent healthy pregnancy.

Bavencio is FDA approved in several indications including Merkel cell carcinoma, urothelial carcinoma, and renal cell carcinoma in certain settings or combinations.

PTSR is the probability, given as a percentage, of a drug progressing successfully from one development stage to the next. The PTSR score considers characteristics like therapy area, indication and molecule type, and is used to calculate a drug’s Likelihood of Approval (LoA), which in this case is now at 41% following a five-point increase after the trial was completed.