Bone MRI Scans Show Improvement; Safety Results Consistent with TASKi2

SOUTH SAN FRANCISCO, Calif., July 23 /PRNewswire-FirstCall/ -- Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced that in the TASKi3 Phase 2b clinical trial in rheumatoid arthritis (RA) patients who had failed to respond to at least one biologic treatment, the group treated with R788 (fostamatinib disodium) did not report significantly higher ACR 20, ACR 50, ACR 70 and DAS28 response rates than the placebo group at three months, and therefore, the trial failed to meet its efficacy endpoints. The objective components (CRP and ESR)* of these ACR scores did show a statistically significant difference; however, the subjective reported response rate components did not as compared to placebo. Although the ACR scores for the R788 group were within the expected range in this patient population, the reported placebo response rates were considerably higher than seen in any other previous study of RA biologic failure patients and rose unaccountably between week 6 (at which point the reported response rates between R788 and placebo were significantly different) and month 3 (when such reported response rates were no longer significantly different).

TASKi3 was the first clinical trial evaluating R788 in which anatomical changes in the patients' wrist and hands were evaluated using Magnetic Resonance Imaging (MRI) and scored using the RAMRIS (Rheumatoid Arthritis Magnetic Resonance Imaging Scoring) system. Those results showed improvements in the treated group versus the placebo group in the Synovitis and Osteitis scores, while the Erosion scores, known to be the slowest to change, showed no significant effect at three months. The most frequent adverse events were as expected from the earlier TASKi trials and appear to be manageable.

Rigel will host a conference call today at 7PM EDT/ 4PM PDT to discuss these results (see conference call details below).

"Our objective with R788 in RA is to position the product after methotrexate and before biological therapies are used. We have shown excellent results in that patient population in our earlier TASKi1 and TASKi2 studies, and we believe that patient population represents the large market opportunity for this product," said James M. Gower, chairman and chief executive officer of Rigel. "In this TASKi3 patient population, biologic failures, we have seen divergent results as sometimes happens in studies with subjective components. However, we are pleased to see excellent results in the objective measures and in the Synovitis and Osteitis MRI scores," he added.

*blood measurements of C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR)

    Efficacy Results
    Treatment  N of Pts     ACR 20       ACR 50       ACR 70     DAS28<2.6
    ---------  --------     ------       ------       ------     ---------
    Placebo          73     27 (37%)      9 (12%)       4 (6%)      6 (10%)
    -------         ---     -------       ------        -----       ------
    100 mg bid      146     56 (38%)     32 (22%)      13 (9%)     15 (12%)
                             p=0.84       p=0.09       p=0.37       p=0.15
    ----------      --- ------------ ------------ ------------  -----------
    p=values compared to placebo
    Note: At 3 months. All patients were on stable doses of methotrexate
          throughout the clinical trial.

    MRI Results
    TASKi3 Mean Change from Baseline in RAMRIS* Scores at Month 3
                  Placebo      100 mg bid         p=values
                  -------      ----------         --------
    Synovitis**     +0.35            -0.52         p=0.038
    ----------      -----            -----         -------
    Osteitis**
     Score          +1.17            -0.19         p=0.058
    ----------      -----            -----         -------
    Erosion Score   +0.94            +0.78          p=0.62
    -------------   -----            -----          ------
    * RAMRIS is a rheumatoid arthritis scoring system utilizing magnetic
      resonance imaging to evaluate abnormalities (synovitis, bone edema
      and bone erosion) in the hands and wrists.  The system was developed
      by OMERACT, (Outcome Measurements in Rheumatology) in 2002, and has
      become a global standard measurement of inflammation and destruction
      in those joints. For these scores a lower value indicates a better
      clinical condition.
    ** Synovitis: inflammation of the synovial membrane lining joints
       Osteitis: inflammation of the bone

Safety Results

Similar to TASKi2, the most common clinically meaningful drug-related adverse events noted in TASKi3 were diarrhea and hypertension. Dose reduction options were pre-specified in the trial protocol and, in cases where doses were reduced, patients generally completed the clinical trial with minimal safety issues.