Five Prime bets up to $452.5M on Inhibrx's cancer antibodies

Five Prime CEO Rusty Williams

Five Prime Therapeutics ($FPRX) is buying to Inhibrx's early-stage cancer R&D, signing a deal worth up to $452.5 million to get its hands on an immuno-oncology project.

Under the agreement, Five Prime will pay $10 million up front to collaborate with Inhibrx on an antibody that activates glucocorticoid-induced tumor necrosis factor receptors, or GITRs, which are proteins expressed by the body's T cells that help galvanize an immune system attack on cancer. Inhibrx is eligible for as much as $442.5 million more--in either cash or Five Prime stock--if the program, now in the lead-selection stage, wins the FDA's coveted breakthrough-therapy designation and comes through on some undisclosed clinical, regulatory and sales milestones.

Five Prime, looking to build out a pipeline of immuno-oncology treatments, said it homed in on GITR as a particularly promising target, pointing to preclinical studies in which agonist antibodies led to tumor regressions, especially when paired with other therapies. And the biotech singled out Inhibrx as an ideal partner thanks to its proprietary antibody system, which Five Prime said allows for GITR activation without the need for Fc receptor binding.

"We believe this program has the potential to create a differentiated, next-generation GITR agonist that may have broad therapeutic application as a monotherapy or in combination with approved checkpoint inhibitors or other therapies, including products in our pipeline," Five Prime CEO Rusty Williams said in a statement.

Five Prime's work in immuno-oncology has attracted some big-name partnerships over the past year. In March, the company inked a $650 million deal with Bristol-Myers Squibb ($BMY) to collaborate on so-called checkpoint inhibitors, treatments that work by removing the brakes on the immune system to kill tumors. Months later, Five Prime signed a $30 million partnership with Bristol-Myers to combine its FPA008 antibody with that company's PD-1-blocking Opdivo. And, in May, Five Prime handed bluebird bio ($BLUE) the rights to some early-stage oncology antibodies for as much as $130 million, giving its partner the raw tools necessary to craft new CAR-T treatments for cancer. The company is also working with GlaxoSmithKline ($GSK) on an early-stage cancer treatment.

- read the statement

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