Shire of the UK said this morning its new attention-deficit hyperactivity disorder drug NRP104 had been deemed approvable by the US Food and Drug Administration, and is on track for a launch in the second quarter of 2007.

The FDA’s notice for NRP104 (lisdexamfetamine dimesylate) was not unexpected, said Shire, as the FDA often requires new drugs for ADHD to be assessed by the US Drug Enforcement Agency to determine the restrictions and monitoring that should be put in place on distribution.

As most drugs to treat ADHD are based on amphetamine-like substances, they are classified according to ‘scheduling’, which determines the level of controls that need to be in placed. The FDA has suggested that NRP104 should be place in Schedule II, and critically has not asked for any additional clinical studies to be carried out.

Schedule II includes drugs that have potential for abuse, but also have accepted medical uses and have their distribution controlled by the DEA.

Once negotiations on the scheduling and a trade name for NRP104 have been completed, Shire should be able to go ahead and launch the product.

NRP104 has been developed by Shire in collaboration with New River Pharmaceuticals of the USA, and is intended as a successor to Shire’s top-selling Adderall XR (mixed amphetamine salts) ADHD product. With NRP104 now looking likely to roll out next year, a lot of the risk associated with Shire in the coming months has been mitigated, said analysts.

Adderall XR is the biggest selling drug in the ADHD arena, with revenues in excess of $730 million last year, up 20%, with a 26% share of the US market. But Shire desperately needs to reduce its reliance on the product: Adderall XR sales were $221 million in the second quarter of this year, out of total revenues at Shire of $440 million.

NRP104 is likely to be well-received because it functions as a prodrug, only becoming active once metabolised so offering a lower risk of abuse and overdose. Meanwhile, Shire has several other ADHD products which are potentially as exciting as NRP104 coming to the market in the next 12-18 months, which will further de-risk the ADHD franchise, according to Navid Malik of Collins Stewart.

In August, Shire settled a long-standing patent battle with Barr Pharmaceutical over the latter’s attempt to market a generic version of Adderall XR. The arrangement between the two companies means Barr cannot market generic Adderall XR in the USA until April 1, 2009, which should give Shire time to switch existing patients to NRP104.

Shire also settled earlier this year with another generics firm, Impax Laboratories, in a deal which allowed Impax to market a generic version of Adderall XR 181 days following Barr's launch. Barr's generic holds first-to-file status in the USA, which means it is entitled to be the only generic on the market for six months after Shire's patents on Adderall XR expire.