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5 questions facing gene therapy in 2021

Three years ago, the Food and Drug Administration granted a landmark approval to the first gene therapy for an inherited disease, clearing a blindness treatment called Luxturna.

Since then, the regulator has approved one more gene therapy, the spinal muscular atrophy treatment Zolgensma, and given a green light for dozens of biotech and pharmaceutical companies to start clinical testing on others. Genetic medicines for a range of diseases, including hemophilia, sickle cell and several muscular dystrophies, appear in reach, and new science is galvanizing research.

But, entering 2021, the gene therapy field faces major questions after a series of regulatory and clinical setbacks have shaded optimism. “The ups and downs of adolescence are on full display” analysts at Piper Sandler wrote in September, summing up the state of gene therapy research.

Here are five questions facing scientists, drugmakers and investors this year. How they’re answered will matter greatly to the patients and families holding out hope for one-time disease treatments.

Are recent high-profile setbacks a warning sign?

The FDA was widely expected last year to approve a closely watched gene therapy for hemophilia A, the more common type of the blood disease. Instead, the agency in August surprisingly rejected the treatment, called Roctavian, and asked its developer, BioMarin Pharmaceutical, to gather more data.

The next day, Audentes Therapeutics reported news came a third clinical trial participant had died after receiving the biotech’s experimental gene therapy for a rare neuromuscular disease. The tragedy brought flashbacks to past safety scares in gene therapy, although the current wave of treatments being tested have generally appeared safe.

A little less than five months later, the gene therapy field is grappling with two more setbacks. UniQure is exploring whether a study volunteer’s liver cancer was caused by its gene therapy for hemophilia B. And Sarepta, one of the sector’s top developers, faces significant doubts about its top treatment for Duchenne muscular dystrophy after disclosing a key study missed one of its main goals.

In each case, the drugmakers involved offered explanations and reasons for optimism. BioMarin still expects to obtain an approval; Audentes’ trial is now cleared by the FDA to resume testing; UniQure thinks it’s unlikely the cancer case is linked to treatment; and Sarepta argued its negative data were the product of unlucky study design.

But taken together, the developments are powerful reminders of both the stakes and uncertainty still facing gene therapy.

All four events also highlighted lingering worries about one-time genetic treatment. In rejecting Roctavian, for example, the FDA seemed to be concerned the impressive benefit hemophilia patients initially experienced may wane over time. The deaths in Audentes’ study, meanwhile, renewed warnings about extremely high doses of gene therapy. Researchers have long watched for evidence that replacing or altering genes may cause cancer to develop in rare instances, particularly after four infants developed leukemia in a gene therapy study in the early 2000s. And Sarepta’s negative findings were surprising because early signs of dramatic biological benefit that didn’t seem to translate into clear-cut functional gains for all patients.

Experts are still confident gene therapy can deliver on its promise. Bu recent events suggest getting there may take a bit longer than some expected.

Has the FDA raised its bar?

“The process is the product,” is an often-used cliche about gene therapy, which are complex treatments with exacting manufacturing standards.

Most of the roughly 60,000 pages in Spark Therapeutics’ application for approval of Luxturna, for instance, involved what’s known in the industry as “chemistry, manufacturing and controls.”

The therapeutic basis for gene therapy, by contrast, is much clearer for many of the rare, monogenic diseases that developers are targeting. If mutations in a single gene lead to disease, replacing or otherwise fixing that gene should have a large benefit.

“Genetic medicine is not industrialized serendipity,” said Gbola Amusa, an analyst at Chardan, contrasting gene therapy with chemical-based drugs. “It often is an engineering question.”

In 2020, the FDA gave ample notice that it’s watching gene (and cell) therapy manufacturing closely. Sarepta, Voyager Therapeutics, Iovance Biotherapeutics and Bluebird bio were all forced to revise their development timelines after the agency asked for new details about production processes.

“The FDA is saying to companies that you’ve got to up your standards,” Amusa added.

For their part, FDA officials have indicated the spate of data requests are a product of the sharply higher numbers of companies advancing through clinical testing.

Are gene editing stocks overheated?

While setbacks have piled up for therapies that seek to replace genes, 2020 was a “transformative year” for therapies designed to edit them, according to Geulah Livshits, an analyst at Chardan.

CRISPR gene editing, already widely recognized as a scientific breakthrough, gained further prestige with the awarding of the Nobel Prize in Chemistry to two early pioneers, Jennifer Doudna and Emmanuelle Charpentier.

But the year also brought important progress from early biotech adopters. Editas Medicine and Intellia Therapeutics, for example, notched CRISPR firsts with use of the editing technology inside the human body.

And CRISPR Therapeutics and partner Vertex showed their experimental therapy, which uses CRISPR to edit stem cells, worked exceptionally well in the first 10 patients with either sickle cell disease or beta thalassemia treated in two early studies.