resTORbio has discontinued the development of RTB101, a TORC1 inhibitor, for the prevention of clinically symptomatic respiratory illness (CSRI) after the drug failed to meet the primary endpoint of the PROTECTOR 1 Phase 3 study.

The US biopharma company was conducting the PROTECTOR 1 clinical trial for assessing the safety and efficacy of RTB101 for the prevention of CSRI in adults, aged 65 and older.

The primary endpoint of the late-stage trial was the reduction in the percentage of patients having clinically symptomatic respiratory illness. This had been defined as illness related to a respiratory tract infection (RTI) based on prespecified diagnostic criteria, irrespective of laboratory confirmation of a pathogen.

The PROTECTOR 1 clinical trial featured 1024 patients who were randomly grouped 1:1 to be subjected to RTB101 or placebo daily once for 16 weeks.  In an analysis of the primary endpoint, resTORbio said that the odds of experiencing a CSRI were 0.44 in the placebo arm, while the odds in the RTB101 cohort were 0.46.

resTORbio will look to undertake detailed analyses of the PROTECTOR 1 clinical trial, including further data on safety and secondary and exploratory endpoints, which are currently not available. The analyses will help the company get insights that may explain the difference in RTB101 activity noted in the PROTECTOR 1 clinical trial compared to the previously held phase 2 studies.

The US biopharma company said that it will continue to develop RTB101 for the treatment of Parkinson’s disease and other aging-related diseases.

Chen Schor – co-founder, president and CEO of resTORbio said: “While we are disappointed in these results, there are extensive preclinical data supporting the potential therapeutic benefit of TORC1 inhibition in multiple aging-related diseases, including Parkinson’s disease, for which we have an active Phase 1b/2a trial of RTB101 alone or in combination with sirolimus.

“Multiple pre-clinical models have demonstrated that inhibition of TORC1 decreases protein and lipid synthesis, increases lysosomal biogenesis and stimulates the clearance of misfolded protein aggregates, such as toxic synucleins, that cause neuronal toxicity in Parkinson’s disease.

“We remain committed to exploring the potential benefits of TORC1 inhibition in patients, and we look forward to the data from our Parkinson’s disease trial, which we expect in mid-2020.”

  Chen Schor, clinically symptomatic respiratory illness, Parkinson’s disease, resTORbio, RTB101, USA