Alfimeprase(Amgen, Inc.)

Recanalization therapies for ischemic stroke have been slow to change clinical practice because of perceived and published risks of hemorrhage associated with lytic administration. We quantified alfimeprase in an acute ischemia-reperfusion model, as compared with recombinant tissue plasminogen activator, with hemorrhagic transformation as the primary endpoint and infarction volume and blood-brain barrier permeability as secondary endpoints.

Five groups were studied in a blinded fashion: alfimeprase at doses of 0.03 (n=8), 0.1 (n=11) and 0.3 mg/kg (n=8); recombinant tissue plasminogen activator at 1 mg/kg (n=9); carrier infused controls (n=9). The middle cerebral artery was occluded for 5 hours followed by removal of the suture for reperfusion. Drugs were infused immediately following reperfusion over a 10-minute period. Approximately 24 hours later, the animals were anesthetized and decapitated, and the brains were rapidly harvested and frozen. Serial brain sections were obtained and inspected for hemorrhages. Infarction and blood-brain barrier permeability were also evaluated in additional experiments in control, 0.1 mg/kg alfimeprase and 1 mg/kg recombinant tissue plasminogen activator-treated rats.

The hemorrhagic transformation frequency, neurological deficit and the mortality rate of alfimeprase were significantly lower than for recombinant tissue plasminogen activator at the 0.03 mg/kg dose and not statistically different at the higher doses. Infarction and blood-brain barrier permeability were not significantly different among control, 0.1 mg/kg alfimeprase and recombinant tissue plasminogen activator.

In this model, alfimeprase, a new fibrinolytic agent, exhibits a profile comparable to recombinant tissue plasminogen activator.

Alfimeprase, a fibrolase derivative with thrombolytic activity produced by recombinant DNA technology, was discovered by Amgen and was in development with Nuvelo for the treatment of stroke and catheter occlusion. However, development has been discontinued. Fibrolase is a zinc-containing metalloendopeptidase that was first isolated from the venom of the Southern copperhead snake, Agkistrodon contortrix contortrix. Alfimeprase directly degrades fibrin to break down clots. Alfimeprase is infused directly into the thrombus (side-hole catheter pushed through the entire clot) via multiple manual pulsed infusions. Alfimeprase degrades fibrin directly and entrapped blood cells are freed. Excess alfimeprase is rapidly inactivated by alpha-2 macroglobulin through an irreversible, covalent interaction. Phase III development of alfimeprase for peripheral arterial occlusion was discontinued based on poor results from the NAPA-2 and SONOMA-2 trials; however, Nuvelo resumed development of alfimeprase in 2007 for stroke and catheter occlusion.Alfimeprase's thrombolytic activity appears to be localized to the site of delivery because it is rapidly inactivated by alpha-2 macroglobulin, a naturally occurring protein in the blood, as it moves away from the site of delivery and into general blood circulation. In January 2002, Amgen and Hyseq Pharmaceuticals (now Nuvelo) entered into a collaboration to develop and commercialize alfimeprase. Nuvelo is to develop the product through clinical trials and Amgen was to be responsible for its manufacture. Both companies were to participate in commercial activities; Amgen was to have the option to lead these. Full financial terms were not disclosed. Further to this agreement, in November 2004 Amgen granted Nuvelo worldwide rights to develop and commercialize alfimeprase in exchange for milestone and royalty payments. In August 2007, Nuvelo decided to focus on core development programmes that it believed would produce the nearest-term proof-of-concept data. As a result of this realignment of organizational expenses, Nuvelo decided to continue to pursue the development of alfimeprase. In February 2003, Hyseq Pharmaceuticals merged with Variagenics Inc. to form Nuvelo Inc. In January 2006, Nuvelo and Bayer HealthCare entered a collaboration to develop and commercialize alfimeprase. Bayer was to commercialize the drug in all territories outside the US, whilst Nuvelo retains full US rights. Nuvelo was to receive other territory royalties and milestone payments to a total of $US385 million. A $US50 million upfront payment will be made to Nuvelo, while Bayer was to be responsible for 40% of the commercialization cost for global development. This partnership was to also develop stroke and deep vein thrombosis therapies. Data from the SONOMA-3 trial fell short of the company's expectations and so Nuvelo has decided to discontinue further development of alfimeprase. Nuvelo previously had decided to resume development of alfimeprase for the treatment of multiple coagulation-related disorders, including acute ischaemic stroke, catheter occlusion (CO) and acute peripheral arterial occlusion.Previously, results from the NAPA-2 (Novel Arterial Perfusion with Alfimeprase-2) trial and SONOMA-2 (Speedy Opening of Non-functional and Occluded catheters with Mini-dose Alfimeprase) phase III trial of alfimeprase in patients with acute peripheral arterial occlusion and catheter occlusion did not meet their primary endpoints. The primary endpoint of the NAPA-2 trial was the avoidance of surgery within 30 days of treatment with alfimeprase, whilst the SONOMA-2 trial's endpoint was the restoration of function at 15 minutes after dosing. In addition, these trials did not meet their secondary endpoints. As a result, Nuvelo and Bayer suspended enrolment in the NAPA-3 and SONOMA-3 phase III trials until additional analysis was complete; the SONOMA-3 trial was re-initiated. Nuvelo concluded that the delivery method for alfimeprase in the treatment of peripheral arterial occlusive disorders was suboptimal. The company closed the suspended NAPA-3 trial and planned to initiate preclinical studies focused on identifying optimized delivery methods in acute PAO in the second half of 2007. Data from the NAPA-2 trial suggested that efficacy could potentially be enhanced by maintaining alfimeprase longer at the site of the thrombus. Nuvelo's multinational phase III programme for peripheral arterial occlusion consisted of the NAPA-2 and NAPA-3 trials. Both trials were randomized, double-blind studies comparing 0.3 mg/kg of alfimeprase with placebo in a total of 600 patients in 100 centres. The primary endpoint of the NAPA-2 trial was the avoidance of surgery within 30 days of treatment; secondary endpoints included safety and pharmacoeconomics such as length of hospital and intensive care unit stay. Results from both trials have been presented. The phase II trial (NAPA-1) was completed in June 2004. This open-label, dose-escalation trial assessed the safety and efficacy of alfimeprase in 115 patients with acute peripheral arterial occlusion and was conducted in centres across the US, Europe and South Africa. Full data from the trial have been presented, which indicated that the 0.3 mg/kg dose appeared to be the optimal dose for investigation in phase III trials. In March 2003, Nuvelo announced the positive results of a phase I trial initiated in the US in July 2002; an IND was transferred from Amgen to Nuvelo in January 2002. In the SONOMA-2 trial, alfimeprase restored catheter function in patients with occluded catheters within 15 minutes with a p-value of 0.022. However, it did not meet the company's target product profile for commercial success with a p-value < 0.00125. Data from a phase II trial were presented at the 46th Annual Meeting of the American Society of Hematology held in December 2004. The study was closed in July 2004 with 55 patients enrolled. Initially the phase II study was to compare three doses of alfimeprase with the approved dose of alteplase in over 90 patients in the US. Nuvelo initiated the phase II CARNEROS-1 (Catheter Directed Alfimeprase for Restoration of Neurologic Function and Rapid Opening of Arteries in Stroke) study of alfimeprase in the treatment of acute ischaemic stroke in June 2007. CARNEROS-1 was a multicentre, open-label, dose-escalation study beginning with doses of 1, 5 and 10 mg of alfimeprase in 100 patients within 3-9 hours of stroke onset. The primary endpoints were recanalization (unblocking) of the occlusive lesion within 120 minutes of treatment, and symptomatic intracerebral haemorrhage. The first patient was dosed in December 2007; enrolment was taking place in the US and Canada. In the US, three patents have been issued relating to alfimeprase; US Patent Nos 6 261 820 (alfimeprase protein sequence), 6 440 414 (formulation of alfimeprase with a zinc stabilizer) and 6 455 269 (methods for localized administration of alfimeprase).