Elusys completes phase 3 clinical program of obiltoxaximab in healthy adult volunteers

Elusys Therapeutics, Inc. (Elusys), a biopharmaceutical company developing antibody therapies to treat infectious disease, today announced it has completed three phase 3 healthy adult volunteer safety studies of obiltoxaximab (ETI-204). Obiltoxaximab is an anti-toxin in development for the treatment of inhalational anthrax and data from these studies support the safety and tolerability of the antitoxin when administered intravenously (IV) at the intended therapeutic dose. The conclusion of these studies marks the completion of Elusys' Phase 3 clinical development program required for filing a biologics license application. Elusys also announced it has completed an additional dose escalation study to evaluate intramuscular (IM) administration of obiltoxaximab. Obiltoxaximab is a potential target for future acquisition into the Strategic National Stockpile, the U.S. government's repository of critical medical supplies for biowarfare preparedness.

"We are very pleased to have completed our phase 3 clinical program, which will provide further understanding of how obiltoxaximab can be used to help protect U.S. citizens in the event of a biowarfare event," said Elizabeth Posillico, PhD, President and Chief Executive Officer of Elusys. "These IV studies included over 300 subjects at the intended therapeutic dose and completed the clinical program required for BLA filing."

The first study was a double-blind, randomized, placebo-controlled expanded safety study that evaluated the safety and tolerability of a single intravenous (IV) dose (16mg/kg) of obiltoxaximab in healthy men and women greater than or equal to 18 years of age. The study enrolled 280 healthy adult subjects and was conducted at four sites in the US. Subjects were randomized upon entry to receive either obiltoxaximab (210 subjects) or placebo (70 subjects). Most adverse events (AEs) reported during the study were mild to moderate in severity. The most frequently reported AEs related to obiltoxaximab were pruritus (itching) and headache. Approximately 5% of subjects in the obiltoxaximab group experienced AEs consistent with hypersensitivity reactions. The most frequently reported hypersensitivity events were pruritus, rash and urticaria.

A second trial was a double blind, randomized, placebo-controlled study that evaluated the safety and tolerability of repeat IV administration of obiltoxaximab (16mg/kg) in 70 healthy volunteers. The study was conducted at two sites in the US. Adult men and women greater than or equal to 18 years of age were randomly placed into one of two different treatment groups upon entry: Group A (35 subjects) received obiltoxaximab on days 1 and 14 and placebo on day 120 of the study; Group B (35 subjects) received obiltoxaximab on days 1 and 120 and placebo on day 14. Most adverse events reported during the study that were considered related to obiltoxaximab were mild to moderate in severity. The most frequently reported AEs considered related to obiltoxaximab were infusion site swelling, infusion site erythema, and infusion site pain. There was no increase in the number AEs related to obiltoxaximab with repeat administration of obiltoxaximab, whether the second dose was administered 14 days or 120 days after the first dose. There were no serious adverse events related to obiltoxaximab administration reported in this study.

The company has also completed an open label, randomized, parallel group drug-drug interaction study to assess the safety and tolerability of obiltoxaximab when given with ciprofloxacin, an antibiotic used to treat anthrax infection after inhalational exposure. Forty healthy males and females between 18 years to 65 years of age were enrolled at one center in the US. The subjects were randomized to one of two treatments: Group 1 (20 subjects) received IV obiltoxaximab (16mg/kg) followed by a single dose of IV ciprofloxacin (400mg), followed by oral ciprofloxacin (750mg) every 12 hours starting on day 2 until the morning of day 9; Group 2 (20 subjects) received IV obiltoxaximab (16mg/kg) alone. All AEs reported during the study that were considered related to obiltoxaximab were mild to moderate in intensity. The most frequently reported AE related to obiltoxaximab was urticaria (hives). Ciprofloxacin had no effect on the pharmacokinetics of obiltoxaximab, and the frequency of adverse events did not appear to increase with co-administration of obiltoxaximab and ciprofloxacin. There were no serious adverse events related to obiltoxaximab administration reported in this study.

"The results from these 3 trials are consistent with findings from previous clinical studies of IV obiltoxaximab and together present a robust safety and tolerability profile for inclusion in our upcoming BLA filing," said Dr. Posillico.

The IM clinical study was a randomized, double-blind, single ascending dose study to assess the safety, tolerability, and pharmacokinetics of single intramuscular doses of obiltoxaximab in adult volunteers. The study enrolled 36 subjects across 4 doses of drug (4, 8, 16 and 24 mg/kg). Clinical conduct has been completed and final analysis is underway.

Inhalation anthrax is a life-threatening infectious disease caused by the bacterium Bacillus anthracis and remains one of the nation's top biowarfare threats. Much of the morbidity and mortality of anthrax can be attributed to anthrax toxins. Inhaled anthrax is often fatal, despite treatment with antibiotics. In the 2001 anthrax letter attacks, inhalational anthrax had a fatality rate of approximately 50% in humans infected even when victims were given antibiotics and supportive hospital care.

Obiltoxaximab is formulated as a solution and is the only anthrax anti-toxin in advanced stages of development that is being investigated for IV treatment and IM prophylaxis administration. The ability to administer an antitoxin via IM injection may provide a valuable alternative to IV injection in an emergency where medical resources and personnel may be limited.