Calistoga Pharmaceuticals closes $40 million Series C financing

Calistoga Pharmaceuticals, Inc., the leader in the development of isoform-selective phosphatidylinositol 3 kinase (PI3K) inhibitors for the treatment of cancer and inflammatory diseases, today announced it has closed a $40 million Series C financing. The financing was led by Quogue Capital, LLC along with existing investors Alta Partners, Amgen Ventures, Frazier Healthcare and Three Arch Partners and new investor Latterell Venture Partners.

“Calistoga Pharmaceuticals has demonstrated significant progress in advancing its promising product development pipeline, including two clinical stage programs”

The funds will be used to advance Calistoga Pharmaceuticals' drug development pipeline of isoform-selective PI3K inhibitors. CAL-101, an oral, delta selective PI3K inhibitor, is currently being evaluated as a single agent in patients with relapsed or refractory indolent non-Hodgkin's lymphoma (iNHL), mantle cell lymphoma (MCL) or chronic lymphocytic leukemia (CLL) and in combination with rituximab or bendamustine in patients with relapsed or refractory iNHL or CLL. Calistoga Pharmaceuticals is planning to advance CAL-101 into a registration program later this year. In addition, the Company will use the proceeds of the Series C financing to advance CAL-263, a delta selective PI3K inhibitor, into Phase 2 studies for the treatment of patients with inflammatory diseases and to advance the company's preclinical programs.

"Calistoga Pharmaceuticals has demonstrated significant progress in advancing its promising product development pipeline, including two clinical stage programs," said James Topper, M.D., Ph.D., Chairman of the Board of Directors and General Partner with Frazier Healthcare. "With over one hundred patients enrolled in clinical trials evaluating CAL-101 over the past year, we are pleased with the impressive clinical results we have observed in these heavily pretreated patients with B cell leukemias and lymphomas, and we look forward to advancing CAL-101 into registration trials."

"We appreciate the validation and support of top tier investors to advance our first-in-class clinical development programs that selectively target the delta PI3K," said Carol Gallagher, Pharm.D., Chief Executive Officer. "We are not aware of any other delta selective PI3K inhibitor under clinical evaluation and plan to rapidly advance these programs to capitalize on our leadership position."

CAL-101, the Company's oral, delta selective PI3K inhibitor, has demonstrated promising anti-tumor activity in a single agent Phase 1 clinical trial involving more than 100 patients with hematologic malignancies. Results presented in June 2010 at the American Society of Clinical Oncology annual meeting demonstrated that single agent CAL-101 treatment in patients with relapsed or refractory indolent non-Hodgkin's lymphoma (iNHL), 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. Overall, CAL-101 was generally well tolerated. A low incidence of hematological toxicity was observed. Some patients had an asymptomatic elevation of transaminases, which was monitorable and reversible following discontinuation of dosing. Most patients resumed CAL-101 at a reduced dose.

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. In addition to CAL-101, Calistoga Pharmaceuticals' pipeline of isoform-selective PI3K inhibitors includes 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.