resTORbio has announced plans to stop the clinical development of RTB101 in the prevention of clinically symptomatic respiratory illness (CSRI) after its Phase III PROTECTOR 1 clinical trial failed to meet the primary goal.

RTB101 is an oral, selective inhibitor of TORC1, which is known to be associated with a decline in the function of various organ systems, including neurologic, immune, and cardiac systems.

The PROTECTOR 1 Phase III trial assessed the safety and efficacy of a 10mg once-daily dose of the drug candidate for 16 weeks in individuals aged 65 years and above during the winter cold and flu season.

It involved a total of 1,024 patients. The randomised, double-blind, placebo-controlled trial did not recruit current smokers or patients with chronic obstructive pulmonary disease.

The primary endpoint was the decrease in the proportion of participants with clinically symptomatic respiratory illness, defined as illness related to a respiratory tract infection (RTI).

The trial did not meet the primary endpoint where the risk of having a CSRI was 0.46 in subjects treated with RTB101 versus 0.44 in those on placebo.

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

“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.”

The company also intends to further analyse PROTECTOR 1 data, including safety and secondary and exploratory endpoints to obtain more information on RTB101 activity in the trial compared to previous Phase II studies.