Pharmacyclics (NASDAQ:PCYC) and development partner Janssen, a division of Johnson & Johnson (NYSE:JNJ), announced on Wednesday that a New Drug Application, or NDA, has been submitted for ibrutinib. The NDA filed with the U.S. Food and Drug Administration requests marketing approval for the drug in the treatment of chronic lymphocytic leukemia/small lymphocytic lymphoma and in the treatment of previously treated patients with mantle cell lymphoma.

Ibrutinib is an oral inhibitor of Bruton's tyrosine kinase, or BTK, an enzyme found in blood cells. Studies have found that inhibition of BTK can help kill malignant white blood cells known as B-cells. If approved, Ibrutinib would be the first oral BTK inhibitor to reach the market in the United States.

Two phase 2 studies have been completed for ibrutinib. Normally, drugs submitted to the FDA for approval must complete three clinical development phases. However, ibrutinib received Breakthrough Therapy Designation for the indications for which marketing approval has been requested, plus another indication, Waldenstrom's macroglobulinemia. This status enables pharmaceutical companies to go through a more accelerated process for the review of drugs that target treatment of serious or life-threatening conditions.

Pharmacyclics and Johnson & Johnson formed a partnership for the development of ibrutinib in December 2011. Under the terms of the agreement, the two companies split development costs, with Pharmacyclics covering 40% of costs and J&J's Janssen unit covering 60%. The companies plan to share any profits for the drug on a 50/50 basis.

Around 113,000 patients in the U.S. have chronic lymphocytic leukemia. More than 15,000 new patients are diagnosed with the disease every year. There are around 5,000 new diagnoses of mantle cell lymphoma in the U.S. annually.

If ultimately approved, ibrutinib could prove to be very successful for Pharmacyclics and J&J. Piper Jaffray estimates that the drug could hit annual sales of more than $4 billion for just the chronic lymphocytic leukemia indication.

Fool contributor Keith Speights has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.