SOMATOGEN’s rHb 414 SECOND-GENERATION RECOMBINANT HEMOGLOBIN IS IN PRECLINICAL

SOMATOGEN's rHb 414 SECOND-GENERATION RECOMBINANT HEMOGLOBIN IS IN PRECLINICAL trials, Somatogen Chairman Charles Scoggin, MD, told an Oct. 1 New York Society of Security Analysts meeting. Somatogen's second version of its recombinant hemoglobin technology has additional modifications to the hemoglobin molecule -- including the "docking" of two molecules together to increase molecular weight -- in an effort to increase the half life of the substance in the bloodstream. rHb 414 is targeted at the chronic blood replacement market, for use in conditions such as chronic anemia and cancer. Chronic blood replacement accounts for about one-third of the total blood replacement market, Scoggin said. Somatogen estimates that its first-generation product, rHb 1.1, has a half-life of 20 to 24 hours; with rHb 414, the firm is hoping for a half-life of five- to-seven days. Phase I trials of rHb 1.1 are expected to be finished this autumn, Scoggin told the NYSSA. "We intend to complete [the second of stage of Phase I trials] this fall. We are currently on target to do that." The second stage of Phase I trials, currently under way, will involve about 18 to 24 healthy volunteers and is primarily being conducted at one clinical trial center. Patients receive doses of up to 25 grams of rHb 1.1, the company's targeted dosage unit. Scoggin said that "ideally" the firm's goal is to be able to administer up to 200 grams of the product. However, in normal volunteers, there is a "volume effect associated with giving hemoglobin. You really can't go up to levels much beyond [25 grams] without starting to remove blood, because you'd literally start to overload the circulatory system," he said. Most people receive two to four units of blood in a transfusion, equivalent to about 50 to 100 grams of rHb 1.1, Scoggin noted. Somatogen is seeking approval of the genetically engineered, recombinant hemoglobin product for acute blood replacement. The leading indication targeted is hemodilution, or replacement during surgery of blood taken from a patient just prior to the procedure and reinfused afterwards. Other possible applications for rHb 1.1 include organ preservation in the transplantation process, treatment of ischemia in conditions such as stroke or heart attack, and treatment of sickle cell anemia and septic shock, Scoggin said. In an effort to eradicate the occurrence of "mild to moderate" fever in patients receiving rHb 1.1, Somatogen made its second modification to the product's purification process as it went into the second stage of dosing trials. Scoggin stressed that "no serious adverse effects" have been observed in the clinical trials and that the firm believes the occurrence of fever is "process-related." In addition, he maintained that since the beginning of clinical trials, FDA has decreased its reporting requirements. Somatogen made a "minor modification" in its purification process "early on" in the first Phase I trial and then saw no relationship between fever and rHb 1.1 dosage, he added. The fever ranged from about 100 to 100.3 degrees and was observed in a "substantial" number of patients, Scoggin said. Doses from 1 gram to 11.5 grams of rHb 1.1 were administered to patients in the first trial, which began in February. In August, Somatogen began construction of a clinical manufacturing facility, which should be operational in about a year. The plant "should be producing commercial material in 1994 to coincide with the pivotal phases of Phase III" trials for rHb 1.1, Scoggin maintained. The facility will have two 3,000-liter fermenters, Chief Financial Officer Timothy Hoogheem said. A larger commercial manufacturing facility is currently "on the drawing board." It will have two 30,000-liter fermenters and be expanded to a capacity of 90,000 liters, for annual production of about 1.2 mil. units, Hoogheem added. Proceeds of $34 mil. from Somatogen's secondary offering, completed in August, will go to the construction of the clinical manufacturing facility and ongoing operations, along with current cash on hand, Scoggin said.