ICOS-Texas Biotechnology L.P. Announces Phase 2b/3 Trial Results for Sitaxsentan
Monday October 21, 7:50 am ET
BOTHELL, Wash., and HOUSTON, Oct. 21 /PRNewswire-FirstCall/ -- ICOS-Texas Biotechnology L.P., a partnership between ICOS Corporation (Nasdaq: ICOS - News) and Texas Biotechnology Corporation (Nasdaq: TXBI - News) announced today top-line results from the STRIDE (Sitaxsentan To Relieve ImpaireD Exercise in Pulmonary Arterial Hypertension) Phase 2b/3 12-week, double-blind, placebo-controlled clinical trial. The STRIDE trial was designed to assess the safety and efficacy of sitaxsentan in patients with NYHA class II, III and IV pulmonary arterial hypertension ("PAH"). The trial enrolled 178 patients who were randomized to either sitaxsentan 100 mg, sitaxsentan 300 mg, or placebo treatment once a day.
The primary endpoint of the Phase 2b/3 STRIDE trial was change in percent of predicted peak VO2 from baseline to week 12. The results showed a statistically significant improvement for the 300 mg dose group compared with placebo treatment (7% relative improvement). The primary endpoint was not statistically significant for the 100 mg dose group. A secondary endpoint was change in 6-minute walk distance from baseline to week 12. The results showed statistically significant improvement for both the sitaxsentan 100 mg and 300 mg groups, compared with placebo treatment. The 6-minute walk test is the most widely used efficacy test for drugs treating PAH. The clinical effectiveness of each of the two sitaxsentan dose groups was equivalent for 6- minute walk distance (9% relative improvement). NYHA class improvement, another important measure that reflects limitations in physical activity, was also statistically significant for the sitaxsentan 100 mg and 300 mg dose groups compared with placebo treatment.
The most frequent adverse events that occurred in patients receiving sitaxsentan, and were more common than in placebo-treated patients, were headache, peripheral edema, nausea, nasal congestion and prolonged clotting time.
Liver abnormalities have previously been recognized as complications related to the endothelin antagonist class of drugs. Liver abnormalities in the STRIDE trial were defined as elevated serum aminotransferase values that were more than 3 times normal. Incidences of liver abnormalities, which reversed in all cases, were 2% for the placebo group, 0% for the sitaxsentan 100 mg group and 10% for the sitaxsentan 300 mg group. When data from the STRIDE trial are combined with data from the extension trial (patients were exposed to sitaxsentan for a maximum of 55 weeks in both studies combined), the incidences of liver abnormalities, which were all reversible, were 5% for the sitaxsentan 100 mg dose group and 21% for the sitaxsentan 300 mg dose group.
Sitaxsentan is a small molecule that antagonizes the action of endothelin, a potent mediator of blood vessel constriction and growth of smooth muscle in vascular walls. Endothelin receptor antagonists may prove to be effective in the treatment of a variety of diseases where the regulation of vascular constriction is important. Sitaxsentan is selective in the targeting of the endothelin A receptor.
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