Spark, Pfizer pass another milestone with impressive results treating hemophilia B

Spark and its partners at Pfizer have now shown that a group of 10 men treated with their gene therapy for hemophilia B can lead normal lives for about a year with no evidence of the life-threatening symptoms that plagued them. And they’re betting that it can last a lifetime.

Their new study published in the New England Journal of Medicine continues to underscore the considerable promise of gene therapy in hemophilia. By introducing a corrective gene, patients are able to make clotting factor in a normal range. All but one no longer need clotting factor. And the sole patient doesn’t need nearly as much of it.

The bleeding rate for these patients was reduced to near zero.

The hard data:

(T)he mean steady-state factor IX activity was 34% of normal (range of 14-81%) following a single administration of investigational SPK-9001. The annualized bleeding rate (ABR) was reduced 97%, from a mean rate of 11.1 events per year before vector administration to 0.4 events per year after vector administration (p=0.02), while factor IX concentrate use was reduced 99 percent (p=0.004).

Matthew Porteus

This study marks another leg of a promising journey for Spark $ONCE and Pfizer $PFE, which in-licensed commercial rights to the drug. But as promising as the results are, it’s not enough to quiet what is certain to be a long running discussion on the durability of the therapy.

“I think we’re definitely on the road” to curing hemophilia, noted Stanford’s Matthew Porteus in an accompanying piece in the NEJM. But we wont know until we actually see how the treatment performs over the long run.

The developers, though, won’t be waiting indefinitely to see if gene therapy like this flags over time. They want to market this therapy in a field where annual clotting treatment costs six-figures a year. And they’ll be looking for a likely jaw-dropping sum for what may or may not be a permanent fix.

At this stage, that looks like a pretty good bet.

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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