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By Nancy Lapid, Health Science Editor

Happy New Year, Health Rounds readers! We start 2024 with a trio of innovative research papers that could lead to practice changing advances. One involves the first partial heart transplant, a procedure that could eventually make many more heart transplants possible in babies. Scientists have also developed a way to fine-tune doses of gene therapies that avoids a damaging immune response; while another group of researchers found that heart drugs knows as calcium channel blockers may one day be able to treat a common form of muscular dystrophy.

In breaking news, see these stories from our Reuters journalists: U.S. FDA approvals bounce back in 2023, sparking hopes of a biotech recovery; Drugmakers set to raise U.S. prices on at least 500 drugs in January; Childhood vaccine doses enter Gaza through Rafah crossing; and Sidney Wolfe, longtime US consumer health watchdog, dead at 86.

A year after performing the world’s first partial heart transplant, surgeons say the procedure will be practice changing for babies waiting for new hearts, like the infant shown here. REUTERS/Havakuk Levison

The first-ever partial heart transplant, done in a baby using just the valves of a donated heart, heralds a paradigm-changing advance for babies who need new heart valves or whole hearts, doctors say.

The transplanted human heart valves will grow as the baby grows, so the child won’t need additional surgeries to implant ever-larger artificial valves as he or she grows into adulthood, according to a report published on Tuesday in JAMA.

The innovation also paves the way for so-called domino heart transplants, in which one donated heart can save two lives. A patient who has healthy valves but needs stronger heart muscle can receive a full heart transplant, while their healthy valves can then be donated to another patient in need.

“You could potentially double the number of hearts that are used for the benefit of children with heart disease,” study leader Dr. Joseph Turek of Duke Health said in a statement.

He estimates that only about 50% of donated hearts are suitable for patients needing whole new hearts, but an equal number of hearts could be used just for the valves.

“If you introduce the donated hearts that weren’t being put to use into the supply chain and add the valves from domino heart transplants, that can create a substantial change,” Turek said.

Turek and colleagues performed the first partial transplant a year ago, in a baby who did not need a whole new heart. Since then, 13 similar procedures have been done at four centers around the world, some of which have been domino heart transplants.

Bringing this innovation to a clinical trial would be the next step to achieving the volume in procedures that would change the availability of hearts by a large amount, he said.

An experimental technique may allow doctors to safely adjust doses of gene therapies while avoiding an unwanted response from the immune system.

The activity of proteins that have been modified via gene therapy needs to be maintained within a therapeutic range to treat or cure a disease. Several methods exist for tuning gene expression in mammal cells, but none of them have been approved for use in humans because they employ proteins that trigger immune responses, according to the researchers.

“This means that the cells that are expressing the therapeutic protein would be attacked, eliminated or neutralized by the patient’s immune system, making the therapy ineffective,” Dr. Laising Yen of Baylor College of Medicine said in a statement.

Instead, Yen’s team has developed a system that turns genes on to different levels on cue using molecules of the antibiotic tetracycline at FDA-approved doses. Their research was reported on Tuesday in Nature Biotechnology.

“Our approach is not disease-specific, it can theoretically be used for regulating the expression of any (gene), and potentially has many therapeutic applications,” Yen said.

To turn on the gene at the desired level, the team engineered a “switch” on the RNA that is activated when it binds to a tetracycline molecule.

When only a small effect from the gene therapy is needed, the patient will only take a small dose of tetracycline, which will turn on the therapeutic gene only a little. If a larger effect of the gene therapy is needed, the patient would take more tetracycline to boost production. To turn off the gene therapy, the patient stops taking tetracycline.

“This strategy… enables us to adjust its production according to disease’s stages or tune to the patients’ specific needs, all using the FDA-approved tetracycline dose,” Yen said.

Calcium channel blocking drugs, widely used to treat heart diseases, hold promise as a future treatment for one of the most common forms of muscular dystrophy, known as myotonic dystrophy type 1, researchers reported on Tuesday in the Journal of Clinical Investigation.

People with myotonic dystrophy have muscle weakness and prolonged muscle tensing (myotonia), making it difficult to relax muscles after use. The disease also affects the eyes, heart and brain, leading to difficulty walking, swallowing, and breathing.

The researchers had earlier discovered that in patients with myotonic dystrophy, cells create abnormal RNA that interferes with healthy muscle function. They have now discovered that these RNA defects impair the movement of calcium and chloride into and out of the cells, a process that ordinarily helps deliver signals from nerve cells telling muscle cells whether to contract or relax.

They have also discovered that verapamil, a calcium channel blocker commonly used to treat high blood pressure, can ease symptoms of the disease in mice with myotonic dystrophy. Before treatment, the mice exhibited severe muscle tensing, muscle weakness, impaired mobility, respiratory defects, and a marked reduction in lifespan.

Upon treatment with verapamil, the mice quickly recovered muscle function and began to resemble their healthy peers.

The authors of an accompanying commentary called the findings “remarkable.” However, they said, “while the results support the modulation of calcium handling as a potential therapeutic target… the reality is more complicated.”

The researchers emphasized that verapamil itself is not an appropriate treatment for myotonic dystrophy in humans due to its potential cardiac side effects, but said the calcium channel is a new therapeutic target for improving muscle function and health in those with the disease.

“Our goal now is to find the appropriate and safe calcium channel blocker that will do the job,” they said, “and we believe it exists.”

This newsletter was edited by Bill Berkrot.

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