Coastal cancer collaboration
SEATTLE—Attracted by a portfolio of small-molecule compounds for the treatment of cancer and inflammatory diseases—and continuing its path toward broadening its oncology portfolio—Gilead Sciences Inc. in late February signed an agreement to acquire Calistoga Pharmaceuticals Inc., a privately held biotechnology company, for $375 million.
Gilead is funding the acquisition, which is expected to close in the second quarter pending regulatory approval and customary closing conditions, through available cash on hand. Gilead—which is based in Foster City, Calif., but also has operations in Seattle, where Calistoga operates—will also pay Calistoga up to an additional $225 million if certain milestones are achieved.
With a portfolio of compounds that selectively target isoforms of phosphoinositide-3 kinase (PI3K)—the pathway shown to be a central signaling pathway for cellular proliferation, survival and trafficking—Calistoga's lead product candidate is CAL-101, a first- in-class specific inhibitor of the PI3K delta isoform.
Four isoforms of the PI3K have been identified: alpha, beta, delta and gamma. The differentiated function and cellular expression of each of these PI3K isoforms offers an opportunity to develop novel therapeutics. Targeting specific isoforms may offer a more selective treatment approach, with the potential to result in an improved efficacy and safety profile, says Calistoga.
CAL-101 is a delta-selective PI3K inhibitor being evaluated for the treatment of hematologic malignancies. PI3K delta is preferentially expressed in leukocytes involved in a variety of inflammatory and autoimmune diseases and hematological cancers. CAL-101 is currently in Phase II studies as a single agent in patients with refractory indolent non-Hodgkin's lymphoma (iNHL) and in combination with rituximab in treatment-naive elderly patients with chronic lymphocytic leukemia (CLL).
"Our team at Calistoga Pharmaceuticals was the first to demonstrate the clinical benefit of targeting the delta isoform of PI3K as a novel treatment approach for patients with CLL and iNHL," explains Carol Gallagher, Calistoga's president and CEO. "We are pleased to join Gilead, as they share our vision that more targeted therapies have the potential to improve the lives of patients with cancer and inflammatory diseases."
According to Dr. Norbert W. Bischofberger, Gilead's executive vice president of R&D and chief scientific officer, the purchase of Calistoga builds on the company's recent acquisitions of CGI Pharmaceuticals and Arresto Biosciences, and serves to further broaden Gilead's pipeline and expertise in the areas of oncology and inflammation. Nathan Kaiser, a spokesman for Gilead, notes that the Arresto acquisition in particular gave Gilead Phase I studies of GS 6624 in solid tumors and in idiopathic pulmonary fibrosis.
"Cancer remains an area of significant unmet medical need, and our increased understanding of the genetic basis of cancer allows for the development of disease-specific targeted therapies," Kaiser says. "We are very encouraged by emerging clinical data for CAL-101, and this compound could represent an advance for the treatment of certain hematological cancers."
Kaiser adds that Gilead may pursue additional purchases with like-minded companies.
"We remain interested in pursuing additional opportunities to acquire companies, drugs or technologies that have the potential to augment or complement our therapeutic areas of focus," he says. "We remain focused on assets with products in Phase I or II, but as always, we reserve the right to be opportunistic, if the asset makes sense."
Calistoga is also working on other selective PI3K inhibitors that are in preclinical development, and may have application in both oncology and inflammatory diseases.
Following the closing of the acquisition, Calistoga's 20 employees will work out of Gilead's Seattle facilities, Kaiser says.