The most common treatment for hemophilia is replacement therapy, where concentrates of the clotting factors (factor VIII for hemophilia A or factor IX for hemophilia B) are administered to the patient. Clotting factors can be obtained from treated human blood sources or recombinant sources. (NHLBI, n.d.) Recombinant factors "are made by inserting the DNA encoding the human protein into mammalian cells grown in culture. They are purified and processed and are non-plasma derived products." (Hemophilia-Information, n.d.) Many patients take replacement therapy on a prophylactic (preventive) basis daily, others apply treatment only in the event of a bleeding event/injury (NHLBI, n.d.). Other treatment options, typically used for specific situations such as prior to dental surgery or to treat active bleeding, include:

Desmopressin (DDAVP), which is a man-made hormone that stimulates the release of stored factor VIII and vonWillebrand factor, while also increasing the level of these proteins in the blood stream, for patients who have mild to moderate hemophilia A. DDAVP is typically administered via injection or nasal spray. (NHLBI, n.d.)

Antifibrinolytic medicines (including tranexamic acid and aminocaproic acid), which may be used in combination with replacement therapy. These agents help keep blood clots from breaking down once formed, and are usually administered in pill form (NHLBI, n.d.)

Currently, there are treatments, as described above. However, scientists are pursuing gene therapy approaches, which in effect would provide a cure. (Mannucci, 2003). For example, this type of treatment is being pursued by researchers in the U.S. And the United Kingdom together with Netherlands-based Amsterdam Molecular Therapeutics, a company that specializes in gene disorders. The study uses as its key mechanism a "vector-gene combination"...

Jude Children's Research Hospital in Memphis. Reportedly, "[t]he gene therapy used in the trial employs adeno-associated viruses (AAV), small viruses that do not cause disease and produce mild immune responses, as vectors (delivery vehicles) to introduce a functioning factor IX (FIX) gene into the liver cells of subjects with hemophilia B. The goal of the trial is to trigger viable, long-term FIX protein production through a single administration of the therapy. This could reduce or even eliminate bleeding episodes in hemophilia B. patients." (Medical News Today).
References

Hemophilia Genetics (n.d.). Retrieved 13 April, 2010 from the Hemophilia-Information.com web site. http://www.hemophilia-information.com/hemophilia-genetics.html

Mannucci PM. (2003). Hemophilia: treatment options in the twenty-first century. J Thromb Haemost 1(7) pp. 1349-55.

Medical News Today. (11 March 2010). Research Update: Gene Therapy for Hemophilia B. Enters New Development Phase. Retrieved from the National Hemophilia Association Web site http://www.hemophilia.org/NHFWeb/MainPgs/MainNHF.aspx?menuid=118&contentid=1490

NHLBI - National Heart, Lung and Blood Institute. (n.d.). How is Hemophilia Treated. Retrieved 13 April 2010 from http://www.nhlbi.nih.gov/health/dci/Diseases/hemophilia/hemophilia_treatments.html

Peyvandi F; Jayandharan G; Chandy M; Srivastava A; Nakaya SM; Johnson MJ; Thompson AR; Goodeve A; Garagiola I; Lavoretano S; Menegatti M; Palla R; Spreafico M; Tagliabue L; Asselta R; Duga S; & Mannucci PM (2006). Genetic diagnosis of haemophilia and other inherited bleeding disorders. Haemophilia 12, Suppl 3, pp. 82-9.

Schoenstadt, A. (2008). Causes of Hemophilia. eMedTV. Retrieved from http://blood.emedtv.com/hemophilia/causes-of-hemophilia.html