Scientists need custom viruses for each gene therapy procedure and there aren’t enough companies making them to keep up with demand.

Gene therapy is hitting a roadblock.

The high-tech therapy is a promising treatment option for numerous life-threatening ailments, including certain types of cancers and inherited diseases like Parkinson’s.

According to the National Institutes of Health, gene therapy is only being tested for diseases that currently have no other form of cure.

Now a kink in the manufacturing process for gene therapy is becoming a big problem for companies hoping to conduct large-scale trials and bring products to market.

Many of these treatments rely on a viral vector — a modified virus — to deliver genetic material into a cell.

The problem lies in one key aspect.

There’s a shortage of these specialized, custom viruses.

Viruses are perfectly suited to carrying a gene to a part of the body with defective cells present.

The faulty cells are then fixed by the healthy gene.

Earlier methods of gene therapy used the adenovirus, which is most notable for causing the common cold.

However, because this virus sometimes elicited an immune response from the body, putting patients at risk, it’s no longer common.

Instead, doctors now use similar viruses called adeno-associated viruses, which don’t provoke the immune system.

Gene therapy is making a large leap from academic research to industrial scale pharmaceutical. Major companies such as Novartis are producing their own gene therapies.

This is causing the demand for viruses to overwhelm current production.

“This was almost entirely an academic activity originally,” said Dr. Barry Byrne, professor of pediatrics and molecular genetics & microbiology, and director of the Powell Gene Therapy Center at the University of Florida.

“Right now, there are only a limited number of studies that can be done with the material that is available. I do think it’s a genuine problem,” he told Healthline.

Part of the problem, as reported by the New York Times, is that there doesn’t appear to be a clear model yet to optimize manufactured virus production.

In some cases, the viruses are developed in-house, as is the case for Byrne at the Powell Gene Therapy Center.

For others, virus production must be outsourced to third parties.

The number of biotech firms now demanding viruses has resulted in queues forming for access.

Some companies, worried about long waits, may pay for queues at different companies to ensure they receive the necessary viruses.

According to the New York Times, Novartis signed up years in advance with Oxford BioMedica to produce their viruses.

MilliporeSigma, a biotech company that makes viruses for drug companies, told the Times they’re “oversubscribed.”

But, in a statement to Healthline, Martha Rook, head of gene editing and novel modalities at MilliporeSigma, said the following:

“MilliporeSigma underwent a major expansion in 2016 to nearly double the production capacity at its Carlsbad, California facility… Given our extensive manufacturing experience, our expanded capacity will allow us to address more of the market imbalance going forward. We are committed to helping our customers bring their treatments to market with high quality, on-time production of viral vectors.”

One of the major problems with the current forms of gene therapy is that there’s no “one-size-fits-all” virus that can be used.

That’s to say, gene therapy targeting the liver would require one set of specialized viruses that couldn’t be used on another part of the body for, say, a neuro-degenerative ailment.

At this point, a single virus that can be universally used to target any cell within the body doesn’t exist.

That makes production a specialized endeavor.

Producing viruses is costly and time consuming — especially as it scales upward.

Byrne added that finding well-trained individuals is also a problematic aspect.

“It’s not actually just facility limitations. Frankly, there’s a shortage of trained personnel who have been involved in this field,” he said.

“Someone may be an expert in vaccine manufacturing, which is probably the most closely related activity, but it’s not exactly the same. It’s like saying I’m a great chef but not a great baker,” he added.

Byrne is hopeful that as Big Pharma steps into the arena, they’ll be able to step up to virus manufacturing.

In addition, he explained, there are also newer methods for viral vector development that exist but aren’t widespread among manufacturers — yet.

For now, the transition between the current model of production and the demand for viral vectors will be a turbulent one.

The best way to proceed in manufacturing also may not be totally figured out either.

“Academic sponsored studies and academic facilities have filled the gap for a while and now it will be necessary for new capacity to come online. How that’s deployed, that’s the next consideration,” said Byrne.