Members of Congress want answers about a multinational drug company's deal to save its patents by handing them off to a Native American tribe.

Last month, Allergan gave the St. Regis Mohawk Tribe six patents that protect Restasis, the company's blockbuster eye drug. The goal is a sophisticated legal strategy to avoid having the US Patent Office proceed with a process called inter partes review, which is a kind of quasi-litigation in which opponents of a patent can try to have them revoked. Lawyers for Allergan are hoping that the principle of sovereign immunity, in which Native American tribes are treated as sovereign nations in certain ways, will protect their patents from government review.

The strategy may well succeed. IPR proceedings against patents held by public universities have been canceled on at least two occasions, when the Patent Trial and Appeals Board held that the universities benefit from sovereign immunity because they are state actors. The St. Regis Mohawk tribe will be paid an annual royalty of $15 million as long as the patents are valid.

The strategy could keep prices high for drugs like Restasis by preventing generic drug companies from challenging the patents and producing their own, cheaper versions. The concept of gifting patents to Native American tribes looks alluring enough that patent-holding companies that routinely sue tech companies, often derided as "patent trolls," may be getting into it as well. One such company has already given patents to a Native American tribe in order to sue Apple.

That move has drawn concern from the House Committee on Oversight and Government reform, which has sent a letter (PDF) to Allergan CEO Brenton Saunders demanding more information about the patent transfer.

"The unconventional maneuver has received considerable criticism from the generic competitors challenging the drug's patents under the process Congress created to enable timelier review of such challenges," write the four congressmen who signed the letter. "The sovereign status of Native American tribes adds time and complexity to contesting the status of the patents in question, because tribes may be immune from the legal claims generic drug makers use to challenge patents and bring less costly drugs to market more quickly."

The letter notes that Allergan's patent on the drug's active ingredient was set to expire in 2014. The same year, Allergan filed more patents extending the drug's patent protection to 2024. Restasis is Allergan's second-best-selling drug and generates almost $1.5 billion in revenue per year.

The committee is concerned about competition in the drug industry and goes on to request several types of documents related to the Restasis deal:

1. All agreements and communications between officials at Allergan and the

Saint Regis Mohawk tribe referring or relating to the Restasis patents,

including but not limited to legal expenses. 2. All analyses conducted in preparation for or relating to any agreements

regarding the Restasis patents, including but not limited to all analyses

relating to past or future trends or projections for market share. 3. All documents and communications referring or relating to the amount of

money received by your company from sales of Restasis through federal

health care programs, including state programs that receive federal funding. 4. All documents presented to the Board of Directors concerning any agreements

regarding the Restasis patents. 5. All documents and communications referring or relating to considerations for

a similar arrangement and transaction for other products.

The letter is signed by committee chairman Rep. Trey Gowdy (R-S.C.) and ranking member Rep. Elijah Cummings (D-Md.), as well as Rep. Dennis Ross (R-Fla.) and Rep. Peter Welch (D-Vt.)

Allergan has been asked to provide the documents by October 17.