Bayer and partner Nuvelo yesterday said they have begun patient enrollment into a second Phase III trial of its clotbuster alfimeprase in peripheral arterial occlusion, after receiving Special Protocol Assessment in the USA. An SPA is an agreement signed with the country’s Food and Drug Administration on trial design and size, which forms the primary basis of an efficacy claim in a marketing application and represents a bid to speed drugs through the regulatory process.

Alfimeprase, which demonstrated the ability to restore arterial blood flow within a four-hour period post-dosing in a recent Phase II dose-escalation study, will now be investigated in two pivotal studies - NAPA 2 and 3 – involving 600 patients with PAO. The primary endpoint in both trials is avoidance of open vascular surgery within 30 days of treatment.

Enrollment in the first, NAPA-2, study is expected to complete in the second half of this year, but Bayer has no plans to rest on its laurels and is also planning studies in stroke (beginning in the second half of 2006) and deep venous thrombosis (in 2007). Meanwhile, alfimeprase - an enzyme that rapidly breaks down blood clots by attacking their internal fibrin scaffolds - is being studied in an ongoing Phase III trial known as SONOMA in catheter occlusion.

Bayer signed up with Nuvelo in January for the development and commercialisation of alfimeprase for all territories outside the USA. Under the terms of the agreement, Nuvelo could get up to $385 million in milestone payments, including a $50 million upfront fee and royalties of 15.0%-37.5%. A launch in Europe and the USA is planned for 2008/9.