XOMA V. CENTOCOR SUIT ON ENDOTOXIN PATENT INFRINGEMENT

XOMA V. CENTOCOR SUIT ON ENDOTOXIN PATENT INFRINGEMENT, filed by Xoma in San Francisco federal court April 17, may create a sense of deja vu for biotechnology patent watchers familiar with the prolonged erythropoietin legal dispute. At stake in the latest case is a lucrative market of 200,000-400,000 U.S. patients who suffer each year from gram negative sepsis bacterial infections -- a market being fought for by Xoma, with its Xomen-E5 and Centocor, with Centoxin. Product license applications are pending on both monoclonal antibody-based anti-endotoxin products. Xoma has a six-month head start on Centocor. The Xomen-E5 PLA was filed in March 1989, Centoxin's PLA in September 1989. Xoma filed suit seeking a declaratory judgment of patent infringement on the same day the Berkeley, Calif.-based biotech firm's patent application for Xomen-E5 was granted by the Patent & Trademark Office. The patent covers the therapeutic use of mammalian-source monoclonal antibodies for the treatment of gram negative sepsis or septic shock. Xomen-E5 is a murine (mouse)-based monoclonal; Centoxin is human-based. Xoma's patent covers the administration of "a therapeutically effective amount of an antilipid A region monoclonal antibody of the IgM isotype which competitively inhibits the binding of the monoclonal antibody produced by the hybridoma cell line ATCC Accession No. HB9081 to purified lipopolysaccharide from the J5 mutant of E. coli as measured by an enzyme immunoassay or other competitive inhibition immunoassay." The suit contends that the product from Malvern, Penn.-based Centocor is covered by the very similar portion of the claim that reads: "...to purified lipid A from the lipopolysaccharide of the J5 mutant of E. coli..." Centocor responded to the suit in an April 17 statement charging that Xoma's action "was intended primarily for public relations purposes." Xoma's lawsuit came just prior to the publication of Centoxin Phase III data in the April 19 issue of the journal Clinical Research and a presentation of results at the May 5 meeting of the American Federation for Clinical Research. Centocor has two patent applications pending. Both were filed in 1983, "at least three years earlier than Xoma," a company spokesperson maintained. He described the Centocor patents as "very broad, very early patents covering the production [and] use of monoclonal antibodies against gram negative sepsis." Centocor has exclusive worldwide licensing rights to the patents, one of which was submitted by the Velos Group in Maryland. Responding to the patent infringement charges, Centocor asserted that it does "not believe that Xoma could have a valid patent that will impact the future commercialization of our product." The response adds a warning that raises the spectre of extended legal wrangling over patent rights: "We intend to assert our own proprietary rights against Xoma at the appropriate time." * The results of Centoxin's Phase III trial show that the MAb-based anti-endotoxin reduced mortality in gram negative bacteremic and septic patients by 38% and demonstrated a 42% reduction in mortality in patients suffering from shock. By comparison, Xomen-E5 has demonstrated a 46% reduction in mortality in gram-negative septic patients; however, it has not shown a statistically significant mortality reduction in shock patients ("The Pink Sheet" Sept. 25, T&G-8). The Centoxin study, conducted by E. Zeigler, et al., of the San Diego-based Sepsis Study Group, found that in 200 patients with gram-negative bacteremia and sepsis, 28-day all-cause mortality was significantly reduced, from 49% in the placebo group to 30% in the Centoxin group. Among those patients with gram-negative bacteremia and shock, mortality was reduced from 57% for placebo to 33% for Centoxin. One concern about the endotoxin products has been potential immunogenicity. There was no detectable human antibody response to Centoxin in any of the patients. Xomen-E5 elicited an IgG response in 54% of patients tested but was asymptomatic.