Pfizer Inc announced enrollment of the first patient in a phase 2b clinical trial of its investigational Staphylococcus aureus (S. aureus) multi-antigen vaccine (PF-06290510) in adults undergoing elective spinal fusion surgery.

The purpose of the study, named STRIVE (STaphylococcus aureus SuRgical Inpatient Vaccine Efficacy), is to evaluate the safety and efficacy of the vaccine to determine if it prevents postoperative invasive S. aureus infections in patients undergoing elective spinal surgery.

Surgical Site Infections (SSIs) are a significant and growing concern. SSIs caused by S. aureus account for approximately 20 per cent of all SSIs in the US, and are associated with an estimated annual treatment cost of $12.3 billion in the US. Patients who suffer such infections due to antibiotic resistant (MRSA) or antibiotic sensitive (MSSA) S.aureus have worse clinical outcomes, including increased mortality in comparison with non-infected patients.

“We are pleased to take this important next step in the development of our S. aureus vaccine,” said Dr. Kathrin Jansen, senior vice president and chief scientific officer of vaccine research and development, Pfizer.

“To date, there is no licensed vaccine available to prevent invasive S. aureus disease. We believe results from this study, if positive, will bring us closer to a potential preventive measure for this challenging disease that is associated with considerable morbidity and mortality.”

The primary outcome of the study, with an estimated enrollment of 2600 subjects, will measure the number of subjects in each treatment group with postoperative S. aureus blood stream infections and/or deep incisional or organ/space surgical site infections occurring within 90 days after elective posterior instrumented lumbar spinal fusion.

Secondary outcomes will also measure postoperative S. aureus blood stream infections and/or deep incisional or organ/space surgical site infections occurring within 180 days after surgery, and postoperative S. aureus surgical site infections occurring within 90 and 180 days after elective posterior instrumented lumbar spinal fusion. Estimated completion period of the study is 2017.

Pfizer’s S. aureus vaccine was granted Fast Track designation by the US Food and Drug Administration (FDA) in February 2014. The Fast Track process facilitates the development and expedites the review of drugs which treat severe conditions and fulfill an unmet medical need. Fast Track designation also enables Pfizer to continue to have ongoing discussions with the FDA on the development of its S. aureus vaccine.

Multi-antigen S. aureus vaccine is designed to prevent a wide-range of clinical disease manifestations, caused by S. aureus, by facilitating killing of the bacteria at the early stages of invasive infection by targeting multiple virulence mechanisms.

Staphylococcus aureus is a leading cause of healthcare-associated infections, resulting in a substantial burden to health care systems. It is a particularly challenging pathogen, with an arsenal of virulence factors that enable host immune evasion and resistance to antibiotics. S. aureus has the potential to induce a wide spectrum of clinical manifestations, ranging from mild skin infections to deep wound and surgical site infections, bacteremia and sepsis, potentially leading to death.