Gilead Sciences Inc. has acquired a 49.9% equity interest in privately held Pionyr Immunotherapeutics Inc., which could receive up to $1.15 billion in potential future milestone payments in the deal.

Pionyr’s Myeloid Tuning technology aims to rebalance the tumor microenvironment (TME) and is designed to treat patients who don’t benefit from checkpoint inhibitor therapies. A significant volume of the TME is composed of myeloid cells, but in some cases they have been hijacked by the cancer. Some help the tumor grow while others stimulate the immune system.

Shareholders of South San Francisco-based Pionyr will receive $275 million when the deal closes, while Gilead receives 49.9% of Pionyr’s common stock and an exclusive option to purchase the remaining equity. Gilead could exercise an exclusive option, once phase Ib antitumor immunity studies of PY-314 and PY-159 are complete, for a $315 million option exercise fee, to acquire the remainder of Pionyr. The date for the closing was left open, referred to as “shortly” by the company.

Gilead is also pitching in to pay for the two clinical trials and other R&D at Pionyr. Last August, Pionyr announced that the lead development candidates, PY-314 and PY-159 targeting TREM2 and TREM1, respectively, were on track to complete IND-enabling studies and are expected to enter clinical development in 2020. With the Gilead deal, the INDs are now targeted to be filed in the third quarter of this year.

Both have demonstrated preclinical efficacy, the company said, suggesting their potential in treating solid tumors in combination with established anti-PD(L)-1 agents. The Myeloid Tuning therapies are meant to enhance antitumor activity as single agents and in combination. Other current immune-oncology approaches include stimulatory T-cell targets, where cells other than T cells can also regulate antitumor response, and checkpoint inhibitors, which are effective only in a small subset of patients.

The therapies involve disabling suppressive myeloid cells to unleash antitumor immunity. PY-314 is for the highly selective deletion of TME myeloid suppressive cells and PY-159 is for stimulating myeloid cells.

Also in the Pionyr pipeline is PI-114, which has gone through the target validation phase and is now into monoclonal antibody generation and validation.

Pionyr is collaborating with Adimab LLC, of Lebanon, N.H., for the option to license Adimab-generated antibodies to Pionyr’s targets.

Pionyr was co-founded by Max Krummel, a professor at University of California, San Francisco’s pathology department, and by Sachdev Sidhu, a former Genentech scientist and now a professor and director of the Toronto Recombinant Antibody Centre at the Sidhu Lab at the University of Toronto, in 2015. Krummel already had an impressive reputation in the immuno-oncology, or I-O, field, having been one of the patent-holders for CTLA4-targeting antibody Yervoy (ipilimumab) from New York-based Bristol Myers Squibb Co., the first checkpoint inhibitor to clear regulatory hurdles.

Pionyr’s president and CEO, Steven P. James, held prior positions as CEO of Labrys Biologics Inc., of San Mateo, Calif. (acquired by Petah Tikva, Israel-based Teva Pharmaceutical Co. Ltd.) and Kai Pharmaceuticals Inc., of South San Francisco (acquired by Thousand Oaks, Calif.-based Amgen Inc.). James joined Pionyr with a group of angel investors in the summer of 2015. At the time, the company was known as Precision Immune.

Last July, Pionyr appointed Alicia Levey as its senior vice president and chief business officer, bringing experience as chief business officer of Tempest Therapeutics Inc. and vice president of business development at Inception Sciences Inc.

In December 2017, Pionyr brought in a $62 million series B. The funding was led by New Enterprise Associates and included Sofinnova Ventures and Vida Ventures, along with Pionyr's existing investors Orbimed, SV Health Investors, Osage University Partners and Mission Bay Ventures.

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