ViroPharma Incorporated announced initiation of a phase 2 clinical study to evaluate the safety and efficacy of C1 Esterase Inhibitor [Human] for the treatment of acute antibody-mediated rejection (AMR) in recipients of donor-specific cross-match positive kidney transplants.

This randomized, double blind, placebo-controlled study will evaluate the safety, tolerability and clinical effect of C1 Esterase Inhibitor [Human] for the treatment of acute antibody-mediated rejection in recipients of donor-specific cross-match positive kidney transplants. The study will enrol 20 subjects (10 study drug/10 placebo), and will be conducted at up to four (4) transplant centres in the United States.  Subjects will be assessed after two weeks of treatment for safety, PK/PD, and clinical effect and again at six months post-transplant for graft function and patient survival.  

"Each year, thousands of kidney failure patients fail to receive a potentially life-saving transplant because of pre-existing antibodies to a prospective donor kidney," commented Marc E. Uknis, M.D., ViroPharma's medical director.  "These antibodies initiate complement-mediated inflammation and damage, better known as antibody mediated rejection, or AMR.  These patients, many of whom have a willing but incompatible live donor, are currently added to the deceased donor wait list and many will die waiting for a transplant. Current clinical therapies deal with removing antibodies from the circulation, but do not address the damage to the transplant caused by complement activation.  We have the potential with C1 esterase inhibitor - a complement inhibitor - to add to the treatment paradigms which could then permit broader access to transplantation for patients with such antibodies."

ViroPharma's C1 esterase inhibitor, commercially known as Cinryze (C1 Esterase Inhibitor [Human]), is indicated for routine prophylaxis against angioedema attacks in adolescent and adult patients with hereditary angioedema (HAE), a rare, debilitating and potentially fatal disease.

Antibody-mediated rejection is a type of organ transplant rejection that occurs when a patient has antibodies circulating in their blood against the donor organ (i.e. donor specific antibodies, or DSA).  These antibodies can activate the body's own defense mechanism, known as the complement cascade, which in turn causes a complement-mediated destruction of the transplanted organ.  Since there is no approved treatment for AMR, many thousands of renal failure patients that have DSA cannot be transplanted.  Furthermore, over time, all transplant patients can develop DSA and could lose their transplant to a chronic version of antibody/complement-mediated rejection of the transplanted organ.

Cinryze is a highly purified, pasteurized and nanofiltered plasma-derived C1 esterase inhibitor product that has been approved by the US FDA for routine prophylaxis against angioedema attacks in adolescent and adult patients with HAE.  C1 inhibitor therapy has been used acutely for more than 35 years in Europe to treat patients with C1 inhibitor deficiency. In the EU, on March 17, 2011., the CHMP adopted a positive opinion for Cinryze for treatment and pre-procedure prevention of angioedema attacks in adults and adolescents with hereditary angioedema (HAE), and routine prevention of angioedema attacks in adults and adolescents with severe and recurrent attacks of hereditary angioedema (HAE), who are intolerant to or insufficiently protected by oral prevention treatments or patients who are inadequately managed with repeated acute treatment. The CHMP positive opinion forms the scientific basis for the European Commission to issue a binding decision for a Centralized Marketing Authorization, which is expected in the second quarter of 2011.

Severe hypersensitivity reactions to Cinryze may occur.  Thrombotic events have occurred in patients receiving Cinryze for routine prophylaxis, and in patients receiving off-label high dose C1 inhibitor therapy.  Monitor patients with known risk factors for thrombotic events.  With any blood or plasma derived product, there may be a risk of transmission of infectious agents, e.g. viruses and, theoretically, the CJD agent. The risk has been reduced by screening donors for prior exposure to certain virus infections and by manufacturing steps to reduce the risk of viral transmission including pasteurization and nanofiltration.  The most common adverse reactions observed have been upper respiratory infection, sinusitis, rash and headache. No drug-related serious adverse events (SAEs) have been observed in clinical trials.

Cinryze is for intravenous use only. A dose of 1000 Units of Cinryze can be administered every 3 or 4 days for routine prophylaxis against angioedema attacks in HAE patients. Cinryze is administered at an injection rate of 1 mL per minute.

ViroPharma Incorporated is an international biopharmaceutical company committed to developing and commercializing innovative products for physician specialists to enable the support of patients with serious diseases for which there is an unmet medical need, and providing rewarding careers to employees.