Rigel Pharma Shares Down Sharply After WAIHA Treatment Trial Data

By Michael Dabaie

Shares of Rigel Pharmaceuticals Inc. fell sharply Wednesday after the company said data from the Forward Phase 3 clinical trial of fostamatinib in warm autoimmune hemolytic anemia, or wAIHA, didn't demonstrate statistical significance in the primary efficacy objective.

Shares fell 53% to 82 cents in afternoon trading.

The company said the study didn't demonstrate statistical significance in the primary efficacy endpoint of durable hemoglobin response in the overall study population.

In a post-hoc regional analysis of U.S., Canadian, Australian, and Western European trial sites, patients treated with fostamatinib had a favorable durable hemoglobin response compared with placebo, the company said. In the Eastern European trial sites, patients didn't, it said.

Chief Medical Officer Wolfgang Dummer said during a conference call after the results that the company believes the results were negatively impacted by a large placebo response rate from patients treated in Eastern European trial sites. The Eastern European patients seemed to differ in some baseline characteristics from other patients, Dr. Dummer said.

Chief Executive Raul Rodriguez said in the call that the study was based on positive results from the company's Phase 2 study, which was conducted solely in the U.S. and "showed a compelling response in its patient population."

"We were surprised, therefore, that the trial did not demonstrate statistical significance in the primary endpoint of durable hemoglobin response in the overall patient population," Mr. Rodriguez said.

"Overall, the study results appear to be negatively impacted by a large placebo response rate in Eastern European clinical sites," H.C. Wainwright analysts Joseph Pantginis and Emanuela Branchetti said in a research note. "Geographic impacts notwithstanding, we remain encouraged by the totality of the results and look forward to the outcome of company discussions with the FDA which management anticipates taking place by 3Q/YE22."

Wainwright maintained its buy recommendation and lowered its price target to $7 from $11.

Rigel said it plans to continue analyzing the data to understand the geographical differences in patient disease characteristics and outcomes and discuss these findings with the U.S. Food and Drug Administration.

The safety and tolerability profile in the Forward trial was consistent with the existing fostamatinib safety database, the company said.

Autoimmune hemolytic anemia is a rare, serious blood disorder in which the immune system produces antibodies that lead to the destruction of the body's own red blood cells. Warm antibody AIHA, the most common form, is characterized by the presence of antibodies that react with the red blood cell surface at body temperature.

Write to Michael Dabaie at michael.dabaie@wsj.com

(END) Dow Jones Newswires

June 08, 2022 14:38 ET (18:38 GMT)

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