Circassia Pharmaceuticals said today it will halt a recently launched registration study of its grass allergy treatment, as well as preparatory work for a dose-ranging study of its ragweed allergy therapy, after its investigational cat allergy immunotherapy failed a Phase III trial.

The company said its cat allergy immunotherapy missed the trial’s primary endpoint by showing itself nearly equal to placebo in reducing subjects’ combined allergy symptom and rescue medication use score from baseline.

“We are surprised and disappointed by these results. Such a dramatic placebo effect was not a feature of our earlier phase II studies,” Circassia Chief Executive Steve Harris said in a statement.We will now rapidly analyze the full dataset, address the implications for our wider allergy pipeline, and provide an update on the development plans for our broader business at our interim results.”

The Phase III trial enrolled 1245 patients aged 12 to 65 years old with moderate or severe allergy symptoms and a cat at home and was conducted in over 100 centers in North America, Europe, and Russia. The study compared a four-dose course of Fel d 1 allergen peptides, two sequential courses (eight doses), and placebo.

The study’s endpoint outcomes were the difference between placebo and active groups 1 year after the start of dosing, with the primary endpoint being the difference in the mean combined Total Rhinoconjunctivitis Symptom Score (TRSS) and rescue medication scores (the Combined Score) between the treatment and placebo groups 1 year after the start of dosing.  Additional prespecified endpoints included a range of symptom, rescue medication, and quality-of-life improvement measures.

All groups had greatly improved Combined Score vs. baseline, with the four-dose course showing a reduction of 58.2%, compared with 59.8% for the eight-dose course and 58.5% for placebo (4 x 6 nmol reduction = 58.2%; 8 x 6 nmol reduction = 59.8%; placebo reduction = 58.5%).

All groups also showed greatly improved TRSS vs. baseline, with the four-dose course decreasing from 14.5 to 5.7 TRSS points, compared with a drop from 14.2 to 5.5 for the eight-dose course and from 14.5 to 5.9 for placebo.

Circassia said it will review the study’s full data and assess whether any other confounding factors affected the outcome, as well as the implications for its allergy portfolio.

The company added that it will also assess whether to continue its “well advanced” Phase IIb trial of its house dust mite allergy product. Circassia will continue a Phase II study of its Circassia’s birch allergy product, which is nearing completion.

Circassia will also continue to focus on rapidly growing sales of its Niox® asthma management products, advancing its pipeline of respiratory products, and establishing its specialty commercial infrastructure in the U.S. and Europe as a platform for strategic growth, Harris said.

Additional details on the company’s development plans and financial position are expected July 28, when Circassia is set to report interim results for the first 6 months of this year.

Investors reacted to the disclosure with a sell-off that sank the company’s share price nearly 65% on the London Stock Exchange, to 95.85 pence as of 9:25 a.m. ET, from its Friday close of 270.30.

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