After the announcement of positive results from the pivotal late-stage field study of its novel drug, AT-001 by Aratana Therapeutics Inc. (NASDAQ:PETX), its stock rose over 26% to $16.50.

The drug is designed to treat osteoarthritis pain in dogs. The study demonstrated that at once-daily dosage, the dogs receiving the drug showed improvement in the pain assessment scores, and had statistically significant results than the placebo arm.

Osteoarthritis is a progressive disease that involves the destruction of cartilage, joint inflammation, and bone changes. It is reported to affect one in every five dogs, making it the most common cause of canine lameness. The market size of the said drug is huge, given that the population of dogs kept as pets in the US alone is expected to reach 83.3 million by the end of 2014.

280 client-owned dogs suffering from osteoarthritis were enrolled in the blinded, placebo-controlled, multi-centre and dosage ranging study. The dogs were randomly divided into two groups, with one group to be treated with AT-001 and the other to be given placebo pills. The study went for 28 days with daily dosage. The drug's effectiveness was examined by standard protocol using a validated owner-assessed pain score.

Ernst Heinen, Head of Drug Evaluation and Development for Aratana Therapeutics, said that the company was very pleased with the results of the study and it has encouraged them to move toward the drug's approval. Aratana Therapeutics M.D., President and Chief Executive Officer, Steven St. Peter, said that the company believes that the drug has promising potential in the “well-established pain market”. He further said that the company hopes to continue its discussions with the US Food and Drug Administration's (FDA) Centre for Veterinary Medicine.