Phase 1b Study of CB-280 for CF Chronic Lung Infections May Open by September

Calithera Biosciences announced plans to open by September a first clinical study of its oral investigational therapy CB-280 in people with cystic fibrosis (CF).

The Phase 1b, dose-escalating trial (NCT04279769) in up to 32 adults with cystic fibrosis and chronic lung infections caused by Pseudomonas aeruginosa was expected to begin enrolling in April, but its launch was pushed back due to the COVID-19 pandemic.

It follows a now completed Phase 1 trial in healthy volunteers that assessed the safety, tolerability, and pharmacological properties of this small molecule treatment for airway disease in CF, the company announced in a press release.

CB-280 is a selective oral inhibitor of the enzyme arginase, which is responsible for converting the amino acid arginine into urea and ornithine. In CF patients, this enzyme is overly active, leading to a shortage of arginine in the lungs, which in turn reduces anti-microbial airway resistance and lung function.

By blocking arginase and increasing the levels of arginine in lungs, CB-280 is expected to improve patients’ lung function and resistance to microbes that cause lung infections, including the bacteria P. aeruginosa.

Patients enrolled in the Phase 1b trial will be randomly assigned to one of four capsule doses of CB-280 (50, 100, 200, or 400 mg), or to a matched placebo, given orally twice-a-day for 14 days.

The study’s main goal is to assess the safety and tolerability of CB-280, based on the incidence and severity of observed adverse events.

Additional study goals include assessing the medication’s pharmacokinetic properties, such as the maximum concentration of CB-280 measure in treated patients’ plasma. (Pharmacokinetics is the study of how a therapy is absorbed, distributed, metabolized in the body, and eliminated. Plasma is the liquid portion of blood that remains after all blood cells are removed.)

Additional patient groups to test intermediate doses of the medication may still be added to the trial’s protocol, depending on safety data obtained in planned dose groups.

Calithera is also planning to launch a Phase 2 trial (NCT04265534) assessing telaglenastat (CB-839), its anti-cancer treatment candidate, in the third quarter of 2020. The trial will evaluate telaglenastat in combination with standard of care in patients with advanced non-small cell lung cancer (NSCLC).

“We continued our positive momentum from 2019 into the first quarter of 2020 … advancing our key clinical development programs,” Susan Molineaux, PhD, president and CEO of Calithera, said in the release.