Gritstone Oncology, the immuno-oncology upstart that has pocketed more than $194 million in venture capital, is going public. The Bay Area biotech is looking to raise up to $80 million in its IPO, which, along with its sizable war chest, will advance its neoantigen cancer treatments and fund the build-out of its manufacturing facility.
The IPO haul will support Gritstone’s planned phase 1/2 combo trial for its lead asset, GRANITE-001 and preclinical and IND-enabling R&D activities for another candidate, SLATE-001, according to an S-1 filed Thursday. The GRANITE-001 trial is slated to start in the second half of this year. Gritstone will test the candidate with Bristol-Myers' Opdivo in patients with common solid tumors, such as metastatic non-small cell lung cancer and gastroesophageal, bladder and colorectal cancers. The two-part phase 1 dose escalation trial will also test GRANITE-001 with systemic Opdivo and localized injection of Yervoy.
Gritstone’s approach involves identifying the tumor-specific neoantigens (TSNAs) an a patient’s tumor cells, using machine learning to determine which candidate is most likely to activate tumor-specific T cells and then treating the patient with personalized synthetic TSNAs. GRANITE-001 is given in two parts—first a priming adenoviral vector, followed by monthly boosters of an RNA vector, each containing the same 20 patient-specific TSNAs.
SLATE-001 uses the same antigen delivery system as GRANITE-001, but instead of personalizing the treatment to each patient, it contains TSNAs that are shared by a subset of cancer patients. It provides an off-the-shelf alternative to GRANITE-001, Gritstone said in the S-1. The company plans to push the treatment into phase 2 in the second half of 2019.
Gritstone burst on the scene in 2015 with a whopping $102 million series A round, following that up in September 2017 with another $97.2 million. In addition to developing its TSNA-based technology, the company has been constructing a personalized immunotherapy manufacturing facility. The 43,000-square-foot industrialized manufacturing facility in Pleasanton, California, will, according to the company, “form the nucleus of Gritstone’s manufacturing program for personalized cancer therapeutics.”
The same day Gritstone filed its S-1, it announced a cell therapy pact with Bluebird Bio, under which the latter handed over $20 million up front in exchange for 10 tumor-specific targets and T-cell receptors (TCRs). Gritstone will use its platform to analyze specific tumor types to find tumor-specific targets and natural TCRs, while Bluebird will apply its cell therapy platforms to these targets. As part of the deal, Bluebird is also investing $10 million in Gritstone and committing to pay “significant” milestones if candidates advance.