Dosing Begins in Phase 1b Trial of GMA301, Antibody Treatment for PAH

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by Forest Ray PhD |

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GMA301 antibody trial

A first patient has been dosed in a Phase 1b trial evaluating the safety and efficacy of GMA301, an investigational antibody for the treatment of pulmonary arterial hypertension (PAH), Gmax Biopharm, the therapy’s developer, announced in a press release.

GMA301 is a humanized monoclonal antibody, meaning it is made by combining antibody fragments from rodents (mice or rats) and people. The rodent component binds to its target within the body, while the human component makes it less likely to trigger an immune reaction. Gmax reports that this is the first antibody treatment to be tested for PAH.

GMA301 targets the endothelin receptor type A. Endothelin causes blood vessels to narrow, and is overproduced in PAH patients.

The Phase 1b dose escalation study (NCT04503733) aims to enroll 36 PAH patients, ages 18 to 75. The trial will last up to 22 weeks (five to six months), during which time patients will be monitored for adverse events, or undesirable side effects. Study investigators will also assess the medication’s pharmacokinetics — how a compound enters, moves through, and leaves the body — and changes in pulmonary vascular resistance and functional capacity.

Patients will be placed in one of three groups, each with 12 participants: nine will receive GMA301 and three a placebo. A different GMA301 dose — 300, 600 and 1000 mg injections — will be tested in each cohort.

The study is currently enrolling at sites in the U.S. and China. More information is available here.

GMA301 previously showed positive safety and a long half-life in a Phase 1a trial conducted in Australia (ACTRN12618000121268) in healthy volunteers (single doses of 75, 200, 500, and 1000 mg were tested). The demonstrated half-life, or how long it takes for a medication to be reduced to half its starting amount, ranged from 500 to 570 hours, or roughly 21 to almost 24 days, suggesting that a monthly dosing regimen is feasible.

A monthly dosing schedule “will substantially improve convenience and compliance of drug use for patients,” Shuqian Jing, PhD, founder and CEO of Gmax, said in the release.

“We are extremely excited … as GMA301 shows superior efficacy in reducing right ventricular pressure and hypertrophy, and pulmonary vascular thickening and preventing vascular remodeling” in preclinical testing done in a cynomolgus monkey PAH model, Jing said. “If human trials confirm these results, we see hope for the first time that PAH can be turned into a manageable chronical disease.”

The company is also conducting another Phase 1 trial in Australia (NCT04505137; an extension of the ACTRN12618000121268 study) in healthy volunteers. This trial is enrolling adults at its one Adelaide site; more information is available here.

The U.S. Food and Drug Administration has designated GMA301 an orphan drug. This status makes it eligible for a suite of regulatory and financial incentives supporting its development and potential to treat a rare disease.