Rigel Pharma (RIGL) Announced Second FIT Phase 3 of Fostamatinib Did Not Meet Primary Endpoint

October 20, 2016 7:02 AM EDT

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Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) announced results for the second of two double-blind studies in the FIT Phase 3 clinical program for fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor, in adult chronic/persistent immune thrombocytopenia (ITP). The primary endpoint in the study was a stable platelet response, defined as platelet counts greater than 50,000/uL of blood on at least four of the last six scheduled clinic visits between weeks 14 and 24 of treatment. In the FIT 2 (Study 048) Phase 3 study, the fostamatinib response rate was 18%, consistent with the recently reported FIT 1 (Study 047) Phase 3 study. In Study 048, one patient in the placebo group (4%) achieved a stable platelet response; therefore the difference between those on treatment and those on placebo did not reach statistical significance (p=0.152) and the study did not meet its primary endpoint. When the data from both studies are combined, however, this difference is statistically significant (p=0.007). Data from both FIT Phase 3 studies and the open-label extension study demonstrates the consistent benefit of fostamatinib in ITP.

Stable Platelet Responders / Total Patients

FIT 1 – Study 047

FIT 2 – Study 048

Combined

Fostamatinib

9/51

18%

9/50

18%

18/101

18%

Placebo

0/25

0%

1/24

4%

1/49

2%

p=0.026

p=0.152

p=0.007

"We believe that the totality and consistency of data from the FIT Phase 3 program, which included two Phase 3 studies and one long-term extension study, strongly supports a clear treatment effect, with a sustained clinical benefit of fostamatinib," said Raul Rodriguez, president and chief executive officer of Rigel. "We are encouraged by these results and believe that the risk/benefit ratio for fostamatinib is positive for patients with chronic/persistent ITP, a population with a serious unmet medical need. As a result, we will continue to pursue this opportunity. Our next step is to seek feedback from the FDA."

In the combined dataset for Study 047 and Study 048, patients who met the primary endpoint had their platelet counts increase from a median of 18,500/uL of blood at baseline to more than 100,000/uL at week 24 of treatment. These patients benefited substantially and typically did so within weeks of initiating treatment, providing early feedback as to whether fostamatinib may be a viable option for treating their ITP. In the combined data sets, the frequency of patients who achieved a stable platelet response was statistically superior in the fostamatinib group versus the placebo group in all subgroup analyses: prior splenectomy or not; prior exposure to TPO agents or not; platelet counts below or above 15,000/uL of blood at baseline, demonstrating that the effect of fostamatinib is consistent across various clinical and treatment backgrounds.

The most frequent adverse events were gastrointestinal-related, and the safety profile of the product was consistent with prior clinical experience, with no new or unusual safety issues uncovered.

FIT Phase 3 Long-Term Extension Study 049

Patients from both the 047 and 048 Phase 3 studies were given the option to enroll in a long-term open-label extension study (Study 049) and receive treatment with fostamatinib. As of June 2016, 118 patients had been enrolled in this study. All the patients who responded to fostamatinib in the parent studies enrolled in Study 049 and had a median platelet count of 96,000/uL of blood in this study. These patients have been exposed to fostamatinib for a median of 13 months through the combined parent and 049 trials.

In addition, there were 43 placebo non-responders from the 047 and 048 studies that enrolled in the 049 study. 36 of these patients had at least 12 weeks of follow-up. Of these, 6 patients (17%, p=0.01) achieved a prospectively defined stable platelet response in the 049 study.

"Given the heterogeneity of ITP, it is currently almost impossible to predict how patients will respond to available therapies, which is why it is so important for physicians and patients to have treatment options," said James B. Bussel, M.D., professor of pediatrics, pediatrics in obstetrics and gynecology, and pediatrics in medicine at Weill Cornell Medicine, and the principal study investigator on the FIT Phase 3 program. Dr. Bussel is also a member of Rigel's advisory/scientific board. "This heterogeneity means that treatments that work by different mechanisms can make important contributions in certain patients, such as those who might be especially responsive to fostamatinib because of its unique mechanism of action. The FIT Phase 3 studies have both demonstrated that fostamatinib provided a robust and enduring benefit for those patients who responded to the drug."

Statement on Financial Position

Rigel expects to report that it ended the third quarter of 2016 with approximately $85.3 million in cash, cash equivalents, and short-term investments, which Rigel expects will be sufficient to fund its operations through the end of 2017. In this forecast, Rigel has allocated substantial funds to continue efforts in preparation of the potential commercial launch of fostamatinib in ITP. Rigel is also continuing to evaluate ex-U.S. partnerships for fostamatinib and other partnering opportunities. As a result of the recent research restructuring, Rigel believes that it has created greater flexibility for its cash runway moving forward.



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