Calistoga Pharmaceuticals Announces Initiation of Phase 2 Trial of Delta-Isoform-Selective PI3 Kinase Inhibitor CAL-101 in

Trial to Evaluate Benefit of Novel Targeted Therapy

SEATTLE--(BUSINESS WIRE)-- Calistoga Pharmaceuticals, Inc., the leader in the development of delta-isoform-selective phosphatidylinositol 3 kinase (PI3K) inhibitors for the treatment of cancer and inflammatory diseases, today announced the initiation of a Phase 2 combination trial of CAL-101, the company’s oral, delta-selective PI3K inhibitor, plus rituximab (Rituxan®) in previously untreated, elderly patients with chronic lymphocytic leukemia (CLL).

“With conventional rituximab-containing chemoimmunotherapy regimens, the chemotherapy agents improve efficacy, but often cause toxicities that are of particular concern in older patients,” said Susan O’Brien, M.D., Professor of Medicine in the Department of Leukemia at the University of Texas MD Anderson Cancer Center and a principal investigator for the new trial. “Because existing agents do not cure CLL and cytotoxic agents commonly result in severe toxicities, there is a substantial medical need for the evaluation of efficacious and well-tolerated new treatments for patients with this life-threatening cancer.”

Approximately 15,000 people in the United States are diagnosed with CLL each year, and the median age at time of diagnosis is 72. Commonly used front-line treatment regimens for CLL, which usually include chemotherapy, often have unacceptable adverse events, particularly among the elderly. The Phase 2 trial will enroll up to 60 patients over the age of 65 with CLL or small lymphocytic lymphoma (SLL). Patients will receive treatment with rituximab, administered in eight weekly doses, together with oral CAL-101, administrated twice daily; they will not take chemotherapy as part of the regimen. Patients will remain on CAL-101 therapy as long as they continue to benefit. The trial is designed to evaluate the safety and clinical activity of the new combination treatment.

“To date, we have noted a profile of substantial clinical activity and good tolerability among the nearly 30 patients at our center who have been enrolled in the Phase 1 trials of CAL-101,” said Ian Flinn, M.D., Ph.D., Director of Hematologic Malignancies Research at the Sarah Cannon Research Institute and an investigator in the new study. “Since rituximab is also very well tolerated, a combination of targeted therapies may provide an efficacious and tolerable new front-line regimen for elderly patients with CLL.”

“This Phase 2 trial is part of our overall strategy to evaluate CAL-101 in CLL and indolent non-Hodgkin lymphoma, both in patients with relapsed or refractory disease and in patients who have not received prior therapy,” said Langdon Miller, M.D., Executive Vice President, Research and Development at Calistoga Pharmaceuticals. “As a first-in-class, delta-selective PI3K inhibitor, we believe CAL-101 has the potential to safely offer a new therapeutic option for patients with lymphoid malignancies, either when given alone or when administered in combination with other active agents.”

In addition to the new Phase 2 combination trial, Calistoga Pharmaceuticals is conducting an ongoing Phase 1 single-agent trial of CAL-101 in patients with relapsed or refractory CLL, indolent non-Hodgkin lymphoma (iNHL), or mantle cell lymphoma (MCL). The company is also conducting an ongoing Phase 1 trial of CAL-101 given in combination with either rituximab or bendamustine (Treanda®) in patients with relapsed or refractory iNHL or CLL. An extension study has been instituted to permit those patients who are deriving clinical benefit past 12 months to continue long-term CAL-101 treatment. Calistoga Pharmaceuticals is currently finalizing plans for registration-enabling trials of CAL-101.

About CAL-101

CAL-101 is a first-in-class inhibitor of the PI3K delta isoform. It is an orally administered small molecule, and exhibits greater than 200-fold selectivity in cell-based assays for the delta isoform as compared to other 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 has demonstrated promising single-agent anti-tumor activity in patients with hematologic malignancies. Interim results are available from an ongoing Phase 1 clinical trial of single-agent CAL-101 in patients with relapsed or refractory CLL, iNHL, and MCL. In patients with CLL, more than 30 percent have had an overall tumor response, with more than 90 percent experiencing a 50 percent or better shrinkage in lymph node burden. In addition, among patients with CLL who had pretreatment thrombocytopenia, the majority showed improvements in bone marrow function as evidenced by increases in platelet counts. In patients with iNHL and MCL, overall response rates have been greater than 50 percent. CAL-101 has been generally well tolerated. Some patients with NHL have had monitorable, reversible elevations of liver transaminases and the majority of patients who had reinitiation of therapy at a lower CAL-101 dose continued without further elevations.

About Calistoga Pharmaceuticals

Calistoga Pharmaceuticals is dedicated to developing targeted therapies to improve the health of patients with cancer and inflammatory diseases. Calistoga Pharmaceuticals has a portfolio of proprietary compounds, led by CAL-101, that selectively target isoforms of PI3K. In addition to CAL-101, Calistoga Pharmaceuticals’ product development pipeline includes other selective PI3K inhibitors that are in early clinical development or are ready for initial clinical trials in patients with inflammatory diseases and cancer. Calistoga Pharmaceuticals is a private company headquartered in Seattle, Washington. For more information, visit the Company’s website at:

Forward-looking Statements

This press release contains statements that are forward-looking, including statements about the development of CAL-101, other selective PI3K inhibitors and the efficacy, potency and utility of our product candidates in the treatment of cancer and inflammatory diseases. These forward-looking statements involve risks and uncertainties, many of which are beyond Calistoga Pharmaceuticals’ control. Known risk factors include, among others: clinical trials may not demonstrate safety and efficacy of any of Calistoga Pharmaceuticals’ drug candidates; any of Calistoga Pharmaceuticals’ drug candidates may fail in development, may not receive required regulatory approvals, or be delayed to a point where they do not become commercially viable. Any of the foregoing risks could materially and adversely affect Calistoga Pharmaceuticals’ business and results of operations. Calistoga Pharmaceuticals does not undertake any obligation to publicly update its forward-looking statements based on events or circumstances after the date hereof.


Rathbun Communications, Inc.
Julie Rathbun, 206-769-9219
[email protected]

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