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Calistoga Pharmaceuticals' CAL-101, an Oral Delta Isoform-Selective PI3K Inhibitor, Demonstrates Clinical Benefit in Patients with Relapsed or Refractory Indolent Non Hodgkin's Lymphoma, Mantle Cell Lymphoma and Chronic Lymphocytic Leukemia

The results presented were from an interim assessment of 106 patients enrolled in the ongoing Phase 1 study of CAL-101 in patients with relapsed or refractory chronic lymphocytic leukemia, indolent and aggressive non-Hodgkin's lymphoma, acute myeloid leukemia and multiple myeloma. Over half of the patients enrolled in the trial were refractory to their last therapy prior to entering the study, and the median number of prior treatment regimens was five. Patients received continuous, twice daily, oral dosing of CAL-101 on a 28-day cycle for up to 12 cycles.

Single agent CAL-101 treatment in patients with relapsed or refractory indolent non-Hodgkin's lymphoma (NHL), mantle cell lymphoma (MCL), and chronic lymphocytic leukemia (CLL) resulted in overall response rates of 57 percent, 67 percent, and 30 percent, respectively. Furthermore, 94 percent of patients with CLL had greater than 50 percent decrease in their lymph node disease, demonstrating a high degree of biologic activity.

The majority of responding patients remain on CAL-101 treatment. The median duration of response is not yet achieved at this interim assessment, although 12 patients have experienced a duration of response of more than 6 months. Three of these patients have completed more than 12 cycles (336 days) of treatment and are continuing to receive treatment with CAL-101 as part of an extension protocol.

Overall, CAL-101 was generally well tolerated. A low incidence of hematological toxicity was observed. Some patients had elevation of liver transaminases, which was monitorable and reversible following discontinuation of dosing. Most patients who experienced an elevation in transaminases resumed CAL-101 at a reduced dose.

"The single agent activity demonstrated by CAL-101 in heavily pretreated patients with NHL and CLL is impressive," said Richard R. Furman, M.D., Weill Cornell Medical College. "This oral, small molecule targeted therapy approach may provide a new paradigm of treatment for patients with lymphoid malignancies."

"As we have treated more patients with CAL-101, we are pleased to see a consistent response in indolent NHL, mantle cell lymphoma, and CLL patients," said Albert Yu, M.D., Chief Medical Officer of Calistoga Pharmaceuticals. "With over a 100 patients now evaluated, we are developing a good understanding of the clinical activity and tolerability of CAL-101."

CAL-101 is a first-in-class inhibitor of the PI3K delta isoform. It is an orally administered small molecule, and exhibits a greater than 200-fold selectivity in cell-based assays for the delta isoform as compared to other class 1 PI3K isoforms. CAL-101 is designed to induce cancer cell death (apoptosis) and to inhibit the signaling pathways associated with cancer cell dependence on the tumor microenvironment.

"CAL-101 continues to show promise as a novel, first in class, treatment for patients with hematologic malignancies," said Carol Gallagher, Pharm.D., Chief Executive Officer of Calistoga Pharmaceuticals. "We look forward to initiating a registration program for CAL-101 later this year."

In addition to CAL-101, Calistoga Pharmaceuticals has a pipeline of isoform-selective PI3K inhibitors including CAL-263, a delta isoform-selective PI3K inhibitor for treatment of patients with inflammatory diseases such as asthma, chronic obstructive pulmonary disease and rheumatoid arthritis.

About Calistoga Pharmaceuticals

Calistoga Pharmaceuticals is dedicated to developing targeted therapy to improve the health of patients with cancer and inflammatory diseases. Calistoga Pharmaceuticals has a portfolio of proprietary compounds selectively targeting isoforms of the PI3K pathway. The Company's most advanced compound, CAL-101, a selective PI3K delta inhibitor, is under clinical evaluation in patients with B cell malignancies. Calistoga is a private company headquartered in Seattle, Washington. For more information, visit the Company's website at: www.calistogapharma.com.

Rathbun Communications, Inc.
Julie Rathbun, 206-769-9219
Julie@rathbuncomm.com