PROTOCOL 
Protocol 
I. BACKGROUND 
I. A. Peripheral artery disease: primary pharmacologic therapy is ineffective for 
patients with critical limb ischemia. 
The clinical consequences of occlusive peripheral arterial disease (PAD) include pain on walking 
(claudication), pain at rest, and loss of tissue integrity in the distal limbs. When the extent and distribution 
of arterial occlusions results in signs and or symptoms of muscle ischemia, patients may be treated by one 
of three approaches. The first, and most conservative, is risk-factor modification with or without a 
program of exercise therapy; this approach is appropriate for patients with mild or moderate claudication. 
The second is non-surgical revascularization (percutaneous transluminal angioplasty [PTA]) which may be 
appropriate for claudication, rest pain, and/or non-healing ischemic ulcers. The third is surgical 
reconstruction, typically involving the use of native vein or prosthetic material to bypass the occlusive 
lesion(s); this option is typically reserved for patients with severe (<100 yards) claudication, rest pain, 
and/or non-healing ischemic ulcers. 
It is noteworthy that a variety of medical therapies have been investigated for patients with 
PAD; while controversy exists regarding die efficacy of medical therapy for patients with mild to moderate 
claudication, there is no evidence to suggest that any medical therapy is efficacious for patients with rest 
pain and/or ischemic ulcers due to PAD 2. With specific regard to medical therapies designed to facilitate 
the development of collateral arteries, Marcus's assessment H, published in 1983 remains accurate today: 
"The effects of many drugs. ..[and]. ..hormones on the functional capacity of native collaterals have been 
examined and in the main, no positive results have been found. In 1979 Schaper wrote: 'I know of no 
pharmacologic agent that has been conclusively shown to increase conductance of pre-existent 
collaterals...' " This very serious limitation in therapeutic armamentarium is compounded by the fact that 
many patients with rest pain and/or ischemic ulcers are poor candidates for either PTA or surgical 
reconstruction. Rest pain and/or ischemic ulcers, for example, are most frequently observed in association 
with occlusive lesions of the popliteal and/or infrapopliteal arteries; for such lesions which exceed 2 cm in 
length, PTA is typically unsuccessful 12. Distal bypass surgery for such patients may be employed 
successfully provided that the arterial circulation of the distal calf and/or foot includes a reconstituted artery 
that is favorable for distal bypass; often times, the arterial circulation of the lower calf and/or foot may be 
unsatisfactory to serve as the distal anastomotic donor site for surgical bypass. When the arterial 
circulation of the distal extremity is unfavorable for either percutaneous or surgical revascularization, and 
conservative measures fail, amputation of a portion of the lower limb may be required. 
The prognosis for patients with chronic critical leg ischemia, i.e. rest pain and/or established 
lesions which jeopardize the integrity of the lower limbs, is often poor. Psychological testing of such 
patients has typically disclosed quality-of-life indices similar to those of patients with cancer in critical or 
even terminal phases of their illness^. It has been estimated that 150,000 in toto 14 require lower limb 
amputations for ischemic disease in the United States per year. Their prognosis after amputation is even 
worse 2; the perioperative mortality for below-knee amputation in most series is 5-10% and for above- 
knee amputation 15-20%. Even when they survive, nearly 40% will have died within two years of their 
first major amputation; a major amputation is required in 30% of cases; and full mobility is achieved in 
only 50% of below-knee and 25% of above-knee amputees . 
These grim statistics are compounded by the lack of efficacious drug therapy. As concluded in 
the Consensus Document of the European Working Group on Critical Leg Ischemia 2, "...there presently 
is inadequate evidence from published studies to support the routine use of primary pharmacological 
treatment in patients with critical leg ischemia..." Evidence for the utility of medical therapy in the 
treatment of claudication is no better 15,16 Consequently, the need for alternative treatment strategies in 
such patients is compelling. 
I. B. Therapeutic Angiogenesis is a Novel Srategy for the Teatment of Critical Limb 
Ischemia 
The therapeutic implications of angiogenic growth factors were identified by the pioneering 
work of Folkman and colleagues over two decades ago 12. Beginning a little over a decade ago 1^, a 
series of polypeptide growth factors were purified, sequenced, and demonstrated to be responsible for 
natural as well as pathologic angiogenesis. 
Recombinant DNA Research, Volume 20 
[317] 
