Pfizer Inc.'s experimental drug for cancer weight loss was shown to help patients regain weight in a mid-stage study, offering fresh promise for treating the dangerous muscle-wasting condition.

In cancer patients, a syndrome called cachexia causes changes in metabolism and appetite. It can lead to the loss of critical skeletal muscle and fat that weakens the body and, in some cases, can make cancer treatments less effective. Studies suggest that as much as 30% of all cancer deaths are caused by cachexia and about 80% of patients with advanced stage cancers are affected by the condition. There are currently no drugs approved to treat it.

Pfizer's drug, called ponsegromab, is a monoclonal antibody that blocks GDF-15, a protein expressed when the body is under extreme stress. High GDF-15 levels in cancer patients are thought to be associated with loss of appetite and nausea, which led Pfizer's scientists to hypothesize that blocking the protein's expression could prevent the onset of cachexia.

The drug was discovered in-house at Pfizer, which has been looking to cancer drugs to drive its next growth chapter. Last year, the company bought cancer drugmaker Seagen Inc. for $43 billion, and investors have been hungry for positive news as its COVID-19 vaccine sales continue to dwindle.

Pfizer enrolled 187 patients with cancer and high levels of GDF-15 in a Phase II study that tested ponsegromab's effect on body weight compared with a placebo. Patients in the trial had non-small cell lung cancer, pancreatic cancer or colorectal cancer, and about 75% of them had progressed to stage 4.

At the highest 400 milligram dose, patients regained about 5.6% of their body weight in 12 weeks, according to results published in the New England Journal of Medicine. Those patients also saw improvements in appetite, physical activity levels and skeletal muscle, according to the findings, which will be presented simultaneously at the European Society for Medical Oncology conference in Barcelona.

Charlotte Allerton, head of discovery and early development at Pfizer, said in an interview that the company hopes ponsegromab will enable weight gain that allows patients to tolerate more treatment and "be more active, which of course will improve their overall health."

Pfizer is discussing development plans with regulatory agencies and aims to begin registration-enabling studies in 2025. The company is also testing ponsegromab in patients with heart failure and high levels of GDF-15. Allerton said the company is exploring other conditions linked to elevated GDF-15, such as chronic kidney disease.