Clinical Trials

At Proteostasis Therapeutics, we are dedicated to discovering novel therapies to treat diseases caused by dysfunctional protein processing, such as cystic fibrosis. Clinical trials – and the people who enroll in them – are a critical component to help us achieve this goal.

Clinical Trial PTI-428-01
A Phase 1 clinical trial of PTI-428, a FDA Fast Track designated investigational oral treatment for cystic fibrosis (CF), is currently underway in the U.S. The randomized, double-blinded, placebo controlled trial will evaluate the safety, tolerability and pharmacokinetics of PTI-428 in adults (18-55 years old) diagnosed with CF.

All adults with cystic fibrosis (18-55 years old) are welcome regardless of their individual gene mutation.

What is PTI-428?
PTI-428 is a unique modulator of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein, called an amplifier, that when used in combination with existing treatments and therapies has shown a consistent positive effect on CFTR protein activity in vitro in pre-clinical studies.

Trial Design
PTI-428-01 is a randomized, double-blinded, placebo controlled trial that evaluates the safety, tolerability and pharmacokinetics of PTI-428 in adults (18-55 years old) diagnosed with CF. The trial consist of two parts: the first part enrolls adults with CF in a single ascending dose (SAD) and in a multiple ascending dose (MAD) treatment group.

The second part of the study evaluates the safety, tolerability, pharmacokinetics and efficacy of PTI-428 in adults diagnosed with CF, including patients actively taking Orkambi® according to label indication.

Now enrolling participants

Trial Eligibility
Participants must meet the following inclusion and exclusion criteria (a full list of trial eligibility
requirements will be evaluated at participating centers):

Inclusion Criteria

• Adult males or females age 18-55 years old, at
the time of informed consent
• Confirmed diagnosis of CF
• FEV1 40%-90% predicted pre-bronchodilator
• Patients on background therapy, such as Kalydeco® or Orkambi®, taken according to label indication
• Non-smoker and non-tobacco user for a
minimum of 30 days prior to screening and for
the duration of the study

Exclusion Criteria

• Participation in another clinical trial or treatment
with an investigational agent within 30 days or 5
half-lives, whichever is longer, prior to Study
Day 1
• History of cancer within the past five years
(excluding non-melanoma skin cancer).
• History of organ transplantation
• History of alcohol or drug abuse or dependence
within 12 months of screening as determined by
the Investigator
• Male and female of child-bearing potential,
unless they are using highly effective methods

What is cystic fibrosis?

Cystic fibrosis (CF) is a life threatening, progressive genetic disease affecting an estimated 70,000-100,000 people worldwide. The cause of CF is attributed to mutations in the gene that encodes CF transmembrane conductance regulator (CFTR), a protein that promotes the transport of salt and water to tissues such as the lungs, skin and pancreas. The defect disrupts healthy ion flow and causes a buildup of thick mucus and bacteria in several organs, resulting in persistent lung infections and the inability for the body to break down food and absorb vital nutrients.

Approximately 2,000 mutations in the CFTR gene have been identified to date, although only 272 CFTR mutations are known to cause CF. While advancements in research and treatments have extended the life expectancy for those living with the disease, CF remains a serious, life-limiting condition with no known cure.

We believe that’s not enough.
Clinical trials – and participation from patients like you – hold the key to one day finding a cure.

PTI Clinical Trials Support Line phone number: 1-866-223-3262
To find a clinical trial site, visit or
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