Shares of Dimension Therapeutics $DMTX were pummeled on Tuesday, after the biotech posted subpar Factor IX scores on its gene therapy program for hemophilia B.
By the numbers: Patients in one cohort taking DTX101 had peak Factor IX (FIX) expression of 13%, 20% and 12% over 4 to 8 weeks, according to investigators. At the 12-week followup, though, the scores had slipped to 5% and 8% in two patients at 12-weeks follow-up, and 7% for the third patient at 7 weeks. “For the low-dose cohort, expression levels achieved 10-11% peak activity, stabilizing between 3-4% at last follow-up.”
Spark Therapeutics, which has a rival gene therapy for hemophilia B, has already boasted that four participants experienced consistent and sustained factor IX activity levels, with a mean greater than 30% of normal. But Spark also has had to contend with evidence of an immune response that has had to be batted back with steroids.
In addition, Dimension reported elevations in alanine aminotransferase (ALT) — evidence of liver toxicity — in 5 of 6 patients, spurring a need to use steroids. One patient in cohort 2 experiencing a grade 4 adverse event due to an elevated laboratory ALT, and the biotech is holding back on dosing cohort 3 until they have a chance to review things with the FDA.
That’s not what analysts wanted to see.
Reported Gena Wang at Jefferies:
DMTX reported HemoB data which appears subpar with 3-8% FIX activity and steroid use in 5/6 pts. While we see limited chance in HemoB with current data, we believe punishment is overdone (trading below cash). HemoA oppt remains somewhat open and we see a significantly different bar for the OTC program (urea-cycle disorder, data could be in 2017). PT lowered to $7 to reflect reduced oppt in hemophilia but maintain Buy rating and we see upside from here.
The comparison between Dimension and its top rival proved unappealing to investors, who slashed Dimension’s shares by about half in mid-day trading.
UniQure has another hemophilia B gene therapy it’s working on, which has also paled in comparison with Spark’s effort. BioMarin, meanwhile, is seen as well out in front with its work on hemophilia A.
“We are encouraged by the apparent efficiency of gene transduction and the early trend we are seeing in sustained FIX activity across both cohorts with our wild-type FIX AAVrh10 vector in patients. We continue to explore the therapeutic window for DTX101 as our data mature and in light of the ALT rises that appear to be associated with a decline in FIX activity,” said Dr. Annalisa Jenkins, MBBS, FRCP, Chief Executive Officer of Dimension.
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