Investors have put $15.5M behind cancer drug startup to revive shelved Hsp90 inhibitor

A cancer pharmaceutical startup called Esanex generated lots of reader interest back in May when it began raising a $15 million round.

The latest U.S. Security and Exchange Commission filing from Esanex (in December) shows that the round was completed with $15.5 million, and today, the Indiana Seed Investment Fund II said it participated in Esanex’s series A with a $500,000 investment.

Managed by life sciences trade group BioCrossroads, the fund has $8.25 million to invest in early stage companies. A statement from BioCrossroads explains that Esanex will put the investment toward a phase 1 study of its oncology drug in patients with solid tumors as well as multiple phase 2 studies.

Here’s what we’ve learned about Esanex since May: It’s apparently a resurrection of Serenex, a North Carolina-based cancer drug company that was acquired by Pfizer in 2008 when it was in phase 1 development. Several former Serenex executives appear to be involved in Esanex and in regulatory filings, Esanex lists its business address as the office of Lilly Ventures, a former Serenex investor. Life sciences investor Intersouth Partners, another Serenex investor, also lists Esanex as a portfolio company.


The drug they’re working with is SNX-5422, an experimental drug that “deactivates” the ability of tumor cells to survive and grow by blocking Hsp90.

Hsp90 is a molecular chaperone protein that guides the integration of many key cancer-causing proteins within cells. It’s been an attractive target for cancer researchers, but one that’s been difficult to capitalize on because of side effects associated with the impairment of normal cellular function. Apparently, Pfizer shelved Serenex’s drug due to ocular toxicity in canine studies. Similarly, AstraZeneca returned the rights of two Hsp90 inhibitors it was developing to their original owner, Infinity Pharmaceuticals, in 2008, and Bristol-Myers Squibb halted development on tanespimycin in 2010.

But the climate for Hsp90 inhibitors today may be more amenable than it was just a few years ago. Last year, Novartis presented results from phase 1 and 2 studies that found its candidate, AUY922, had an acceptable safety profile and produced “manageable” side effects. Swiss company Debiopharm is also developing an Hsp90 inhibitor, Debio 0932, and delivered positive safety results in a study last year.

It appears that Esanex has acquired the rights to SNX-5422 and is preparing to take it to phase 1 safety trials in patients with blood cancers and solid tumors.

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