Japanese biopharmaceutical company Sosei says that its candidate treatment for rheumatoid arthritis, AD 452, has failed to meet primary and secondary efficacy endpoints in a Phase IIb clinical trial.

The company said that, as a result of the disappointing results, it has decided to discontinue development of the compound for RA and to remove it from its pipeline.

The 308-patient trial, carried out at sites in Europe and the USA, looked at the efficacy, safety and tolerability of three strengths of AD 452 administered once daily for 12 weeks to adult subjects with active rheumatoid arthritis despite a background therapy of methotrexate. The primary efficacy endpoint was a 20% improvement in signs and symptoms of the disease – known as an ACR20 response – at week 12.

At 12 weeks in the AD 452 treatment groups, 36% with a 9mg dose, 40% with 18mg and 40% with the top dose of 36mg had achieved ACR20 compared to 32% in the placebo with methotrexate background group. There was no statistically significant difference between the treatment groups and placebo.

AD 452 was a novel small molecule disease modifying anti-rheumatic

drug (DMARD), designed to inhibit the activity of inflammatory cytokines and so reduce joint inflammation and destruction, pain and preserve mobility.