By Brian Gormley | Kansas City, Kan.

Aratana Therapeutics Inc. wants to be dogs’ best friend.

Looking to profit fromconsumers’ willingness to spend on their pets’ medical care, Aratana plans next year to launch clinical trials of two animal-health drugs that could earn U.S. regulatory approval in 2015. Clinical studies of an osteoarthritis drug fordogs and an appetite-stimulating medicine for canines will begin next year,said Linda Rhodes, Aratana’s chief scientific officer.

Americans will spend $52.8 billion on their pets this year, according to an estimate by the American Pet Products Association. That includes $13.5 billion for veterinary care and $12.5 billion for supplies and over-the-counter medicine, according to the association.

Aratana, whose investors include MPM Capital and Avalon Ventures, is one of a few venture-backed start-ups looking to cash in on this market. Others include Putney Inc., ofPortland, Maine, which has raised capital from Safeguard Scientifics Inc. and NewSpring Capital to develop generics used in pets. Another, Rapid Diagnostek Inc., is developing a handheld diagnostic to detect bacteria, viruses and biomarkers. Investors in the Hudson, Wis., company include NEW Capital Fund.

Dogs and cats get many of the same diseases that humans do, but often there’s no drug for their condition, said Aratana’s Dr. Rhodes, who is also a veterinarian. For example, human treatments for anemia have been available for many years, but there’s no equivalent for dogs and cats, she said. Instead of developing treatments for pets, animal-health companies historically have concentrated more on “production animals,” such as cattle, she said.

That’s changing as consumers have begun to treat pets more like family members, according to Aratana. At one time, dogs and cats spent most of their time outside, but increasingly, they’re living indoors which is boosting their life expectancy, according to Aratana’s newly appointed chief executive, former MPM Managing Director Steven St. Peter.

Instead of euthanizingpets when they get sick, consumers are paying thousands of dollars for medical treatments or procedures. It’s not uncommon for pet owners to spend $4,000 or $5,000 to repair the knee of a dog that needs anterior cruciate ligament surgery, according to Dr. Rhodes.

Unlike human pharmaceuticals, which are covered by medical insurance, animal-health products aren’t likely to be blockbusters, according to Dr. Rhodes. But animal-health drugs will be far less costly to develop, she said. The U.S. osteoarthritismarket for dogs is worth roughly $200 million today, she said. Aratana aims to claim a piece of that market.

Private-pay markets, like animal health, appeal because there are no concerns about the ability of a company to persuade Medicare or insurance companies to reimburse for a product, according to Dr. St. Peter.

Aratana sources drugs by licensing animal-health rights to products that are being developing for human use. It licensed animal-health rights to its osteoarthritis drug, an EP4 receptor antagonist, from Japanese company RaQualia Pharma Inc., for example. There’s also opportunity to acquire assets that animal-health concerns havechosen not to develop themselves, Dr. St. Peter said.

Aratana’s second product is a drug that mimics the ghrelin hormone to stimulate eating. It’s difficult to give intravenous nutrition to pets or to get sick animals to eat, said Dr. Rhodes. Aratana’s product could help pets with cancer and other conditions that rob them of their appetites, she said.

Aratana has been adding to its team as it gears up for pivotal clinical studies. In addition to Dr. St. Peter, it has named Louise Mawhinney its chief financial officer, a newly created position for Aratana, which formed in 2010. Ms. Mawhinney previously held the same title with life sciences companies such as Ikonisys Inc., Helicos BioSciences Corp. and ArQule Inc.

Aratana, based in Kansas City, Kan., plans to acquire additional drugs and to raise additional financing as needed, according to Dr. St. Peter. The company, which has raised a total of $30.5 million, rounded up a $15.5 million Series B round in November of 2011, bringing in new investors to join previous backers Avalon, MPM and Cultivian Ventures. The new investors included Middleland Capital, Kauffman Foundation and Hall Family Foundation, Dr. St. Peter said.