Rigel shares sink on arthritis drug concerns

Shares of South San Francisco-based Rigel dropped 38 percent Monday after the company reported Phase IIa results of arthritis drug R788. There was a disparity between results in patients tested in the U.S. and those tested in Mexico. In addition, some study subjects developed hypertension and elevated liver enzymes while on the drug, although, TheStreet reports, the hypertension goes away when the drug is stopped. For its part, Rigel said other RA drugs eventually approved by the FDA have also had different results in Mexico.

Several analysts think investors may have overreacted to the data given the current market conditions. "While investors' shoot first ask questions later' mentality is understandable in the current environment, we believe upon greater analysis of the data, the selloff may prove myopic," wrote Susquehanna Financial Group's Derek Jellinek.

- see this report from TheStreet