Rigel's R788 Drug Improves RA Symptoms

Forty-three percent of the patients treated with the 100 mg dose of R788 improved their RA symptoms by 50% compared with 19% of placebo patients, while another 28% of these R788 patients improved by 70% compared with just 10% of placebo patients.

All of the efficacy results were statistically significant in favor of R788. Patients treated with 150 mg of R788 once a day also improved but generally not as much as the lower dose of the drug.

Increases in blood pressure tied to treatment with R788 emerged as the most worrisome side effect in a previous phase II study of the drug, so this most recent study was designed to more closely measure the drug's affect on hypertension.

RA is a chronic disease requiring patients to take drugs for the rest of their lives, so long-term safety is critically important.

The mean increase in blood pressure from baseline at six months was approximately 1 mmHg for patients treated with 100 mg of R788 twice a day. About 23% of these patients had blood pressure medicines adjusted or in some cases started during the course of the study, compared with 7% of placebo patients.

Other side effects related to R788 included infections and diarrhea.

"We now have a much better understanding of R788's safety profile and believe that the observed side effects may be effectively managed," said Elliott Grossbard, chief medical officer for Rigel, in a statement.

Rigel shares were rising 8.4% to $12.18 in Thursday morning trading.