Rain Therapeutics has reported initial findings from the Phase II basket clinical trial of its milademetan (also called RAIN-32) to treat mouse double minute 2 (MDM2)-amplified advanced solid tumours.

The single-arm, multicentre, open-label trial is designed to assess the efficacy and safety of milademetan as a single agent in 65 advanced or metastatic solid tumour patients.

Such patients who are refractory or not tolerant to standard-of-care treatment and have wild-type p53 and a prespecified minimum MDM2 gene copy number are part of the trial. 

As of 26 October this year, the trial enrolled 17 subjects. 

The objective response rate as evaluated by RECIST criteria is the primary endpoint of the trial. 

Response duration, disease control rate, progression-free survival by investigator evaluation, overall survival, and growth modulation index comprise the secondary endpoints.

According to the findings, two unverified cases of partial responses (PRs) were seen in the trial, with 34% and 30% tumour regression for pancreatic and lung cancer, respectively.

Two subjects with biliary tract and breast cancer experienced favourable activity, with tumour regression of 29% and 27%, respectively, and are currently receiving the treatment. 

The therapy also provided an anti-tumour effect in heavily pre-treated, refractory subjects who had previously received a median of four treatments.

Milademetan’s safety profile so far is in line with those seen in the Phase I trial.

A lead product candidate of the company, milademetan is an oral small molecule MDM2-p53 complex inhibitor.

Rain Therapeutics co-founder and CEO Avanish Vellanki said: “We are encouraged by the preliminary observations from the MANTRA-2 trial. 

“Treatment with milademetan led to tumour regression in patients previously treated with a multitude of therapies across a range of cancers. 

“We look forward to expanding this dataset as the trial continues to enrol.”