Pivoting From IPO, Syndax Inks Combo Trial Deal With Merck

Xconomy Boston — 

Syndax Pharmaceuticals sidestepped an IPO a few months back when it found its cancer drug, entinostat, might have a benefit it didn’t originally anticipate. Now the Waltham, MA-based company is putting that thesis to the test through a deal with Merck.

The two companies announced this morning that they’ll run a Phase 1b/2 clinical trial testing Syndax’s entinostat with Merck’s (NYSE: MRK) so-called “checkpoint inhibitor” cancer drug, pembrolizumab (Keytruda), in patients with either advanced non-small cell lung cancer or melanoma. Financial terms weren’t disclosed, but Merck and Syndax will start enrolling patients in the second half of the year. They could also exercise an option to extend the pact to a Phase 3 study if all goes well.

The trial has two parts: a Phase 1b portion that’ll test the safety of entinostat when combined with Merck’s drug; and a Phase 2 study to see if the drug can effectively treat patients with advanced lung and skin cancers.

This is the type of deal that Syndax CEO Arlene Morris hinted to Xconomy recently was coming. Syndax was planning to take itself public last year, aiming to use the cash partly to fund a late-stage study of entinostat in breast cancer. The drug is what’s known as a selective inhibitor of histone deacetylases, or HDACs, and Syndax has been developing it as an add-on to hormone therapy for breast cancer patients. The idea is that entinostat can make tumor cells more vulnerable to hormone therapy, enabling patients to delay shifting to chemotherapy.

Syndax is still pursuing that strategy—data are expected in 2017, and it’s won a breakthrough therapy designation from the FDA for entinostat in breast cancer—but another opportunity unexpectedly opened up too. A preclinical study published in the Proceedings of the National Academy of Sciences last year showed that entinostat might boost the effectiveness of two types of checkpoint drugs—PD-1 and CTLA-4 blockers, which help the immune system recognize tumors. PD-1 inhibitors (like Merck’s pembrolizumab) and CTLA-4 blockers (such as Bristol-Myers Squibb’s ipilimumab (Yervoy)) are among the first in a new wave of cancer treatments that harness the immune system, rather than just nuke tumors and healthy tissue like chemotherapy.

Morris told Xconomy in February that the data steered Syndax away from an IPO. “We thought we ought to step back from the financing process and figure out where that takes us,” she said at the time.

Syndax instead cut a $100 million licensing deal with the Japanese drug firm Kyowa Hakko Kirin, pulled the IPO in January, and started eyeing the mix-and-match game for cancer immunotherapy. Drug companies have been joining forces, running combination trials testing checkpoint inhibitors with various other drugs, looking for the best pairings to boost their abilities.

Morris said in February that Syndax would soon announce such a deal, and ponder a return to the IPO queue down the road. It checked the first of those two boxes this morning.

“We hope that entinostat in combination with [pembrolizumab] may build upon the enormous promise of immunotherapy in treating multiple forms of cancer,” she said in a statement.