By Matthias Blamont PARIS (Reuters) – A major French hospital group has chosen a cheap copycat version of a top-selling drug for treating its patients with rheumatoid arthritis, Crohn’s disease and psoriasis in a victory for a new type of medicine known as biosimilars.    In a document seen by Reuters, the central purchasing agency for the Assistance Publique – Hôpitaux de Paris (AP-HP) said on Friday it had decided to buy the biosimilar version of infliximab from Hospira , after the company offered a discount of some 45 percent to branded Remicade. AP-HP caters for nearly a quarter of the country’s population and the tender decision will allow the copycat to make significant inroads in the French market. Hospira, which is being acquired by Pfizer , sells its drug under the brand name Inflectra.