EnhancedBio’s lead product candidate, Borestrant (ZB716, fulvestrant-3-boronic acid) is a first-in-class, small molecule steroidal oral selective estrogen receptor degrader (SERD) which is currently under clinical development for the treatment of patients with ER+/HER2- locally advanced or metastatic breast cancer.

ER+/HER2- breast cancer relies on the estrogen receptor (ER) for tumor growth and survival and affects approximately 70% of all breast cancers diagnosed. Despite treatment advances, the currently approved therapies including endocrine agents and the only approved SERD;Fulvestrant have certain limitations that create an opportunity for the development of a differentiated candidate. We have developed Borestrant to have a potentially superior product profile with convenient oral administration.

Borestrant is structurally analogous to fulvestrant where boronic derivatives of phenolic compounds significantly increase oral bioavailability by avoiding first-pass metabolism. Borestrant, minimizes the metabolic inactivation and clearance that prevent fulvestrant from accessing target tissues. Nonclinical (IND – enabling) studies confirmed that Borestrant retains full binding affinity of the steroidal moiety of fulvestrant while minimizing glucuronidation and sulfation.

We are currently conducting a Phase 1/2 clinical trial with Borestrant in patients with ER+/HER2- locally advanced or metastatic breast cancer (NCT04669587). We have initiated the Phase 1 portion of the trial in June 2021 and plan to progress to the Phase 2 part in the second half of 2022.