Proteostasis to Test Personalized Treatment with Novel CFTR Modulators in Europe

Three investigative therapies by Proteostasis Therapeutics — PTI-801, PTI-808, and PTI-428 — showed potential to treat cystic fibrosis (CF) patients ineligible for approved CFTR modulators after patient-specific lab models produced promising results that support a future clinical trial.

Funded by the EU’s initiative HIT-CF (Human Individualized Therapy of CF), this early study was conducted on patient organoids, which are miniaturized organ models derived from patient cells.

Based on the positive results, a clinical trial in adult CF patients is expected to start in 2020. If successful, the trial results may serve as the basis for a marketing authorization application in Europe in 2021.

With the help of CF-Europe (a patient organization) and the European Cystic Fibrosis Society Clinical Trial Network (ECFS-CTN), HIT-CF has been recruiting adult CF patients to collect tissue samples and create organoids, three-dimensional organ models grown in the lab.

Organoids mimic several characteristics of the organ from which they are derived, and are genetically identical to the donor. As such, they allow researchers to study biological processes and response to treatments in an environment that closely resembles human organs. As organoids are basically human cells cultured outside the body, they are said to be ex-vivo models.

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The idea is to screen treatment candidates in the lab using intestinal organoids, or mini-intestines, obtained from rectal tissue (biopsies) of patients, which are collected through a quick and painless procedure. Then, based on how the organoids respond to each therapeutic candidate, a group of patients will be selected to enroll in a clinical trial.

Because the organoids can help determine the therapeutic candidate most likely to give the best results, researchers can personalize treatments for each patient before starting the trial.

So far, intestinal organoids from more than 300 patients have been created, of which 65 have been used to test Proteostasis’ potential CFTR modulators.

“Proteostasis is honored to have been invited to participate in the HIT-CF project, and is the only company in the group with a combination of novel CFTR modulators being tested ex-vivo. We are very enthusiastic about the progress of the study,” Geoffrey Gilmartin, MD, chief medical officer of Proteostasis, said in a press release.

The positive results obtained on organoids support the launch of a clinical trial called CHOICES — Crossover trial based on Human Organoid Individual response in CF – Efficacy Study — that will test the potential treatments on patients whose organoids responded favorably to the agents.

The study will also evaluate if organoids are good models to identify promising CF therapies, that is, if the responses measured on organoids translate to potential clinical benefits in patients, as reflected by lung function tests (FEV₁) or sweat tests.

CHOICES will be a placebo-controlled, double-blind study that includes an eight-week treatment period, plus six months of constant dosing.

The study includes Proteostasis’ three candidate CFTR modulators, specially intended for patients who carry rarer CFTR genetic defects. All three compounds have different modes of action. PTI-801 works as a CFTR corrector, PTI-808 is a CFTR potentiator, and PTI-428 is a CFTR amplifier.

The trial is planned to start in mid-2020, with its first data anticipated for the end of 2020.

If moving forward, CHOICES will become the first trial based on personalized medicine for CF patients.

“The inequality in access to CFTR modulators is an acute problem across Europe where 1 in 5 individuals do not have a F508del mutation [the most common CF-causing mutation]. In addition, drug reimbursement policies are leading to an ever-growing gap between patients who do, and those who do not have effective treatment options,” said Christiane De Boeck, Work Package Leader at HIT-CF.

“At HIT-CF Europe, we believe that novel strategies such as personalized medicine and development of new treatment options are central to addressing the inequality of access across the continent. We are thrilled with these initial results and look forward to providing additional updates,” De Boeck added.

Gilmartin said that in Europe more than 2,300 adult CF patients are ineligible for approved CFTR modulators, and therefore excluded from participating in clinical trials.

“This project’s proposed personalized medicine approach is paving a potential new way to develop and provide access to novel CFTR modulators for patients with the most dire need for treatment options that target the cause of the disease. Additionally, based on an individual patient’s disease phenotype, and not just the genetic designation, this approach could also create a new path towards more effective treatment for all people with CF,” Gilmartin said.

Proteostasis is also running a clinical trial evaluating a combination of the three candidate therapies for the treatment of CF patients who have at least one copy of the F508del mutation in the CFTR gene.