With two cases of Grade IV graft-vs.-host-disease in cancer patients, ViaCell Inc. suspended enrollment in a Phase I trial of CB001, its cord blood stem cell product.

The goal of the trial is to evaluate safety in 10 patients, but the study protocol called for a suspension if two of the patients experienced aGVHD. Eight have completed their treatment.

"We are hopeful this is a temporary suspension," said Marc Beer, president and CEO of Cambridge, Mass.-based ViaCell. "We are fully committed to working diligently with the FDA to find a path forward."

The company is reviewing the two cases and all relevant data with the FDA and the institutional review boards in hopes that it can resume enrollment. The news sent ViaCell's stock (NASDAQ:VIAC) downward by 21.6 percent, or $1.39, on Monday. It closed at $5.05.

ViaCell is developing CB001 to provide regeneration of blood and immune systems in cancer patients receiving hematopoietic stem cell transplantation. Patients that need the therapy usually are very ill.

"It is important to realize the therapy that we're developing is a rescue therapy where no or limited options exist for these patients," Beer said in a conference call.

Acute GVHD is a known side effect in transplantation. It occurs when bone marrow, peripheral blood or cord blood from another person is transplanted into the patient. The transplanted cells recognize the recipient tissue as foreign. Both patients in the Phase I trial who experienced aGVHD have recovered and left the hospital.

Beer said that aGVHD occurs in up to 80 percent of all transplants, and Grades III and IV occur in 10 percent to 40 percent of cases. Nevertheless, ViaCell agreed to suspend the trial if two patients receiving its transplants experienced the condition.

"As we advanced CB001 into the clinic, it was our belief that we should maintain very conservative safety parameters because of the specific nature of the clinical protocol that we are using," Beer said.

CB001 is a single-dose therapy that could replace bone marrow and other crude cell mixtures used in hematopoietic stem cell transplants. It consists of a purified population of stem cells isolated from umbilical cord blood and multiplied using ViaCell's Selective Amplification technology.

The Phase I trial, which began in December 2003, has included adults and children older than age 12 who have undergone high-dose chemotherapy and radiation treatment. Patients with advanced stages of leukemia and myelodysplastic syndrome who were in need of a hematopoietic stem cell transplant and were unable to find a suitable donor were eligible to participate.

In preclinical studies, CB001 was shown to contain an expanded population of hematopoietic progenitor cells that, when transplanted into immunocompromised mice, produce healthy blood and immune cells.

Beer said it is too early to tell if CB001 was the cause of the two cases of aGVHD.

"In the literature, cord blood transplants demonstrate less GVHD than adult cells, historically," Beer said.

Amgen Inc., of Thousand Oaks, Calif., is collaborating with ViaCell on the program, and can opt into a joint venture development agreement based on future clinical data.

Aside from CB001, ViaCell is testing a cord blood-derived stem cell for acute myocardial infarction. It also markets its Viacord umbilical cord blood preservation product, which is being used mostly for pediatric bone marrow transplants. And it is developing Viacyte, which is used to preserve and store human eggs in order to extend a woman's fertility.

Incorporated in 1994 under the name t. Breeders Inc., ViaCell changed its name in April 2000 after acquiring Viacord Inc., a private umbilical cord blood-banking business. The company conducted the first initial public offering of 2005, raising $52.5 million in January through 7.5 million shares at $7 apiece. (See BioWorld Today, Jan. 24, 2005.)

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