What happened

Biotechnology start-up Sigilon Therapeutics (NASDAQ:SGTX) is getting beaten down after announcing a clinical hold for its experimental hemophilia drug. Investors worried testing might not resume hammered shares of the clinical-stage biotech stock 23.4% lower as of 12:55 p.m. EDT on Friday.

So what 

Last September, Sigilon Therapeutics began a clinical trial with its lead candidate, SIG-001. This complicated therapy is made of human cells engineered to express high levels of factor VIII (FVIII) for hemophilia A patients who can't produce their own.

Frustrated investor looking down at a computer.

Image source: Getty Images.

Without frequent infusions of factor replacement therapy, hemophilia patients risk uncontrolled bleeding events that can be fatal. The sudden appearance of inhibitors to FVIII is a dangerous complication that reduces the effectiveness of replacement therapy for hemophilia A patients. 

Shares of Sigilon Therapeutics are falling today because the third patient given SIG-001 in an ascending dose study developed FVIII inhibitors. This led the FDA to place a clinical hold on the only clinical trial the company is running at the moment.

Now what

As human cells encapsulated by protective spheres, SIG-001 was supposed to be a semi-permanent way for hemophilia A patients to reduce their reliance on factor replacement therapy. Sigilon Therapeutics will try to convince the FDA its candidate wasn't responsible for the sudden appearance of FVIII inhibitors for the patient in the study.

If Sigilon can't get its hemophilia program restarted, the company's new lead candidate will be one of two lysosomal storage disorder treatments currently in preclinical testing. SIG-005 is a candidate for the treatment of mucopolysaccharidosis type 1, and SIG-007 is a potential treatment for Fabry disease. 

Trying to catch this falling biotech stock could be hazardous to your portfolio. The company finished March with $179 million in cash after burning through $19 million during the first quarter of 2021. With zero candidates in active clinical trials, it could be years before we know if Sigilon has the slightest chance of producing a commercial-stage drug.

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