Health Highlights: Feb. 23, 2021

Trial of Gene Therapy for Sickle Cell Disease Halted

A clinical trial of a new gene therapy for sickle cell disease that's shown promise has been halted after two participants were diagnosed with cancer.

Therapy developer Bluebird Bio said a patient who was treated five years ago developed myelodysplastic syndrome, a form of cancer that's often a precursor to leukemia, while another developed acute myeloid leukemia, The New York Times reported.

Though it isn't yet clear what caused the cancers, one possibility is that the disabled virus used to deliver the gene therapy damaged crucial DNA in blood-forming cells in the patients' bone marrows. That would be the worst-case scenario, said Dr. John Tisdale, head of the cellular and molecular therapeutics branch at the National Heart, Lung and Blood Institute.

But there is also the likelihood that both cancers were caused by a powerful drug, busulfan, which is used to clear bone marrow to make space for new cells modified by gene therapy. Busulfan is known to raise blood cancer risk, Tisdale noted.

Muddying the issue even further is the fact that people with sickle cell disease are known to have an increased risk of leukemia, even without treatment. Still, no one would expect two patients in a small trial to get the disease, the Times said.

The news is a disappointment for those who hoped a cure for sickle cell disease -- which mainly affects Black Americans -- was on the way.

"It feels like the sickle cell disease community just can never get a break," Dr. Melissa J. Frei-Jones, a researcher at the University of Texas School of Medicine in San Antonio, told theTimes.

"My other concern is that the Black community will lose faith or trust in research studies again after it has taken the medical community so long to even regain some degree of trust," she added.

COVID-19 Vaccines Adapted to Fight Variants Won't Require Long Clinical Trials: FDA

Long clinical trials won't be needed to prove the effectiveness of approved COVID-19 vaccines that have been adapted to protect against variants of the new coronavirus, the U.S. Food and Drug Administration said Monday.

Instead, vaccine developers will be asked to conduct small clinical trials such as those required for annual flu vaccines, The New York Times reported.

The recommendation was among a number of new documents released Monday by the FDA, including how antibody treatments and diagnostic tests might need to be altered to respond to coronavirus variants.

Experts are growing increasingly concerned about how the variants may hinder or reverse progress against the pandemic, the Times reported.

"The emergence of the virus variants raises new concerns about the performance of these products," acting FDA Commissioner Dr. Janet Woodcock said in a statement. "We want the American public to know that we are using every tool in our toolbox to fight this pandemic, including pivoting as the virus adapts."

Most makers of approved COVID-19 vaccines or candidate vaccines in late-stage trials have said they plan to adapt their vaccines to tackle variants, the Times reported. The Moderna and Pfizer vaccines use mRNA technology that the companies have said can be used to alter the existing vaccines within six weeks, although testing and manufacturing would take longer.

Moderna has begun developing a new version of its vaccine that could be used as a booster shot against a virus variant that originated in South Africa, known as B.1.351, which seems to weaken the effectiveness of the existing vaccines.