Proteostasis Therapeutics, a biopharmaceutical company developing small molecule therapeutics to treat diseases caused by dysfunctional protein processing such as cystic fibrosis (CF), announced that the company has filed an Investigational New Drug (IND) application with the FDA for PTI-808, its cystic fibrosis transmembrane conductance regulator (CFTR) potentiator. Proteostasis plans to initiate a phase I study of PTI-808 in healthy volunteers in July.

“While potentiators are an established part of CF therapy, there remains significant room for improvement in this critical component of therapy, and we believe PTI-808, with potential once a day dosing regimen, offers the potential to fill this gap,” said Meenu Chhabra, president and chief executive officer of Proteostasis Therapeutics. “Each component of our potential triple combination therapy is now clinical stage, with active and ongoing clinical development programs for both PTI-428, an amplifier, and PTI-801, a new generation corrector. With the filing of an IND for the potentiator PTI-808, the third and final piece of our triple combination, we have reached an important milestone in assembling PTI-NC-733. Pending positive results from ongoing clinical trials with PTI-428 and PTI-801, we expect to initiate a trial combining all three proprietary CFTR modulators before the end of 2017.”

By the end of June, Proteostasis expects to report preliminary data from multiple ascending dose (MAD) cohorts of two different CF patient populations: CF subjects receiving PTI-428 or placebo in addition to Orkambi as their background therapy for seven days and CF subjects receiving PTI-428 as their sole CFTR modulator therapy or placebo for seven days. After a washout period, patients on Orkambi background therapy who were enrolled in the 7-day dosing MAD cohort are eligible to enroll in a 28-day clinical study for PTI-428.

Proteostasis is currently conducting a 14-day MAD phase I study of PTI-801 in healthy volunteers in the U.S., to be followed by dosing in CF patients. If positive results are achieved in the Company’s PTI-428 and PTI-801 programs, Proteostasis intends to initiate a dose range finding (DRF) study at the end of 2017 in an F508del homozygous population who are not taking Orkambi. The study design is expected to include DRF of PTI-808 with fixed dose combination of PTI-428 and PTI-801 in a triple combination also known as PTI-NC-733.