(Adds Dyax CEO, analyst comments)
By Lisa Richwine
WASHINGTON, Feb 2 (Reuters) - U.S. drug reviewers are questioning data supplied by Dyax Corp DYAX.O to back an experimental drug to treat a rare swelling disorder, documents released on Monday said.
Analysts and investors, however, appeared optimistic about the drug’s prospects and the company’s shares rose 2.4 percent.
A Food and Drug Administration advisory panel meets on Wednesday to evaluate the drug, ecallantide, as a possible treatment for hereditary angioedema.
“Issues identified in the phase 3 studies suggest that there is a lack of consistent and substantial evidence to support the efficacy claim of ecallantide,” FDA statistical reviewers said in a summary prepared for the panel.
Dyax shares were up 8 cents to $3.44 in afternoon trading on Nasdaq. Ecallantide, also known as DX-88, is the lead product candidate for the company.
Cowen and Company analyst Phil Nadeau said the advisory panel meeting could be “somewhat contentious” but he expected the outside experts to recommend approval.
“None of the issues appear like they will doom the drug,” Nadeau said in a research note.
Hereditary angioedema, or HAE, is an inherited disorder that causes painful swelling of the skin, intestine, mouth and sometimes the throat. The throat swelling can be life-threatening.
Two Dyax studies compared symptoms four hours after patients received injections of ecallantide or a placebo.
In a preliminary analysis, FDA reviewers noted differences between the 52 patients originally enrolled in one of the studies, known as EDEMA4, and another 44 patients added later.
The latter group showed improvement in symptoms, the agency reviewers said. But the effectiveness for the original group was not statistically significant, which means the results could have been due to chance, FDA staff said.
Those analyses “call into question the robustness of the data,” Sally Seymour, deputy director of the FDA division that reviews pulmonary and allergy drugs, wrote in a Jan. 9 memo.
In an earlier Dyax study called EDEMA3, effectiveness was not statistically significant when reviewers looked at the entire group of patients assigned to get the drug or a placebo, Seymour said.
The memo also noted allergic reactions in 13 percent of ecallantide patients, compared with 10 percent who got a placebo. An FDA clinical reviewer, in a separate memo, said the risks were acceptable with appropriate steps to reduce harm.
Dyax, in its own summary prepared for the panel, said its studies showed “ecallantide is an effective and safe treatment needed by patients who suffer from acute attacks of HAE.” There are no FDA-approved treatments for managing acute attacks now.
Dyax Chief Executive Gustav Christensen said the data backed ecallantide as a beneficial therapy for a debilitating disease.
“So far we are optimistic and looking forward to what the panel has to say,” Christensen said in an interview.
Christensen pointed to the FDA clinical reviewer’s memo, which said Dyax data supported the product’s effectiveness in patients 18 and older.
Seymour’s memo, however, said the clinical review was completed before the agency performed the analysis that raised questions about the EDEMA4 findings.
The agency will consider the advisory panel’s input before deciding whether to approve ecallantide. The agency usually follows panel recommendations. A final decision is expected by March 23. The proposed brand name for the drug is Kalbitor.
The summaries from the FDA and Dyax were posted on the agency's website here. (Reporting by Lisa Richwine; editing by Dave Zimmerman and Brian Moss)