Shares of Cambridge, Mass.-based AVROBIO plunged more than 50 percent on Monday after the company provided an updated look at its gene therapy for Fabry disease that showed promise for the treatment, but also raised some concern for investors.
Citing interim data, Avrobio announced that the first two patients in its Phase I study of its AVR-RD-01 gene therapy treatment continued to “demonstrate AGA enzyme activity above the diagnostic range for classic Fabry disease 18 months and six months.” The company said that the first patient is no longer receiving enzyme replacement therapy. For the patients on the treatment, that was the good news.
Geoff MacKay, president and chief executive officer of Avrobio, touted the results of the treatment for the first two patients.
“We are encouraged by the AGA enzyme activity we are seeing after treatment with AVR-RD-01 in the first two patients with Fabry disease in the Phase 1 study. Both of these patients have AGA activity that remains above the diagnostic range for males with classic Fabry disease, and all patients will continue to be followed for assessment of long-term durable response. We are especially pleased that patient 1 was taken off ERT in mid-July and remains off,” MacKay said in a statement.
Avrobio’s AVR‑RD‑01 is an ex vivo lentiviral gene therapy that is designed as a one-and-done treatment. The therapy works by inserting the GLA gene that encodes functional α‑galactosidase A (AGA), the enzyme that is deficient in Fabry disease. By inserting the GLA gene, the therapy should enable continued AGA production and distribution to tissues and organs. From the initial data, that appears to be happening with AVR‑RD‑01.
However, what has investors concerned is not the results of the AGA enzyme activity, rather it was the fact that four patients saw a drop in vector copy number in peripheral blood. VCN refers to the average number of copies of the lentiviral-vector inserted gene that are integrated into the genome of a cell. While Patient 1 has been taken off the enzyme replacement therapy, his VCN was 0.1. Patient 1 began the study with a VCN of .7. Patient 2 had a VCN of .4 and began with a 1.4. The other two patients also saw a similar decline. That’s what caused share prices to plunge on Monday – wiping out significant gains the company’s stock has made since its initial public offering this past spring when it brought in in $99.7 million.
On Monday, shares fell from Friday’s closing price of $51.80 per share to $25.13.
In separate news, Avrobio announced that it will initiate a Phase I/II trial in Canada to test its lentiviral gene therapy treatment AVR-RD-02 for Gaucher disease. This therapy is designed to permanently integrate the GBA gene that encodes functional glucocerebrosidase, the enzyme that is deficient in Gaucher disease, to enable continuous GBA production and distribution to tissues and organs.
Additionally, the company reported first-patient information from a Phase II trial testing AVR-RD-01, data from the first patient shows AGA plasma enzyme activity was 2.74, but the VVCN was .5.
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