167. A Phase 1b, Randomized, Double-blind, Placebo-controlled, Multiple-ascending Dose Study to Investigate the Safety, Tolerability, and Pharmacokinetics of DSTA4637S in Patients with staphylococcus Aureus Bacteremia Receiving Standard-of-care Antibiotics

Abstract Background New treatment approaches for complicated Staphylococcus aureus bacteremia (SAB) are needed. DSTA4637S is a THIOMABTM antibody-antibiotic conjugate consisting of an engineered human IgG1 monoclonal antibody that binds to wall teichoic acid at the surface of S. aureus, a protease-cleavable linker, and a novel rifamycin class antibiotic, dmDNA31. This Phase 1b study assessed the safety, tolerability, and pharmacokinetics of DSTA4637S in patients with complicated SAB. Methods Multicenter, double-blind, placebo controlled, multiple-ascending dose clinical trial. Patients 18–79 years old with complicated SAB requiring at least 4 weeks of IV anti-staphylococcal standard-of-care (SOC) antibiotics were randomized to receive 4–6 doses of 15, 45, and 100 mg/kg IV DSTA4637S or placebo (6 active:2 placebo) every 7 days in combination with SOC antibiotics. Patients needed ≥ 1 blood culture positive for S. aureus collected within 120 hours prior to randomization. Patients were followed for 120 days after the end of treatment. Results Twenty-five patients with complicated SAB (bone & joint, n=14; endocarditis, n=5; other endovascular, n=5; pneumonia, n=1) were randomized and received 1–6 doses of study drug (19 active:6 placebo). Nine patients (36%) had MRSA. Ten patients completed ≥4 doses of DSTA4637S. The most common treatment-related adverse events were infusion-related reactions (IRRs) (5/19), and abnormal serum color (5/19)/skin discoloration (3/19 (due to dmDNA31). IRRs were not dose-dependent and were reversible with supportive care. Ten of 19 patients (40%) discontinued study drug (9 DSTA4637S,1 placebo); 4/19 (21%) due to IRR. DSTA4637S recipients showed no dose-related changes in laboratory values or vital signs vs. placebo. Observed exposures (Cmax and AUC) were lower in patients immediately after dosing compared to a prior study in healthy volunteers; minimal accumulation occurred. No obvious trends in exploratory bacterial and inflammatory biomarkers were observed between treatment groups. Conclusion DSTA4637S in patients with complicated SAB demonstrated increased IRRs and decreased exposure compared to healthy volunteers, highlighting the importance of Phase I studies of novel treatments in infected SAB patients and not simply healthy controls. Disclosures Jeremy Lim, PharmD, Roche (Employee, Shareholder) Nicholas Lewin-Koh, PhD, Genentech (Employee) Tom Chu, MD, PhD, Genentech (Employee) Sharon M. Rymut, PhD, Genentech (Employee, Shareholder) Aklile Berhanu, PhD, Genentech, Inc. (Employee, Equity interest (Stock/Stock Options)) Montserrat Carrasco-Triguero, PhD, Genentech (Employee) Carrie C. Rosenberger, PhD, Genentech (Employee, Shareholder) Wouter L. Hazenbos, PhD, Genentech (Employee) Loren G. Miller, MD, MPH, genentech (Grant/Research Support) Vance G. Fowler, Jr., MD, MHS, Achaogen (Consultant)Actavis (Grant/Research Support)Advanced Liquid Logics (Grant/Research Support)Affinergy (Consultant, Research Grant or Support)Affinium (Consultant)Allergan (Grant/Research Support)Ampliphi Biosciences (Consultant)Basilea (Consultant, Research Grant or Support)Bayer (Consultant)C3J (Consultant)Cerexa (Consultant, Research Grant or Support)Contrafect (Consultant, Research Grant or Support)Cubist (Grant/Research Support)Debiopharm (Consultant)Destiny (Consultant)Durata (Consultant)Forest (Grant/Research Support)Genentech (Consultant, Research Grant or Support)Integrated Biotherapeutics (Consultant)Janssen (Consultant, Research Grant or Support)Karius (Grant/Research Support)Locus (Grant/Research Support)Medical Biosurfaces (Grant/Research Support)Medicines Co. (Consultant)Medimmune (Consultant, Research Grant or Support)Merck (Consultant, Research Grant or Support)NIH (Grant/Research Support)Novadigm (Consultant)Novartis (Consultant, Research Grant or Support)Pfizer (Grant/Research Support)Regeneron (Consultant, Research Grant or Support)Tetraphase (Consultant)Theravance (Consultant, Research Grant or Support)Trius (Consultant)xBiotech (Consultant) Jose M Miro, MD PhD, GENENTECH (Consultant, Scientific Research Study Investigator, Advisor or Review Panel member) Jessica A. Couch, PhD, Genentech (Employee, Shareholder) Melicent C. Peck, MD, PhD, Genentech (Employee)