Development of Bisphosphonate-Conjugated Antibiotics to Overcome Pharmacodynamic Limitations of Local Therapy: Initial Results with Carbamate Linked Sitafloxacin and Tedizolid.

Emmanuela Adjei-Sowah,Charles E Mckenna,Karen L De Mesy Bentley,Gowrishankar Muthukrishnan,Shuting Sun,Elysia Masters,Jennifer H Jonason,Chao Xie,Frank H Ebetino,Jason Weeks,Yugo Morita,Yue Peng,Edward M Schwarz,X Eric Hu,Philip Cherian

doi:10.3390/antibiotics10060732

Abstract

The use of local antibiotics to treat bone infections has been questioned due to a lack of clinical efficacy and emerging information about Staphylococcus aureus colonization of the osteocyte-lacuno canalicular network (OLCN). Here we propose bisphosphonate-conjugated antibiotics (BCA) using a “target and release” approach to deliver antibiotics to bone infection sites. A fluorescent bisphosphonate probe was used to demonstrate bone surface labeling adjacent to bacteria in a S. aureus infected mouse tibiae model. Bisphosphonate and hydroxybisphosphonate conjugates of sitafloxacin and tedizolid (BCA) were synthesized using hydroxyphenyl and aminophenyl carbamate linkers, respectively. The conjugates were adequately stable in serum. Their cytolytic activity versus parent drug on MSSA and MRSA static biofilms grown on hydroxyapatite discs was established by scanning electron microscopy. Sitafloxacin O-phenyl carbamate BCA was effective in eradicating static biofilm: no colony formation units (CFU) were recovered following treatment with 800 mg/L of either the bisphosphonate or α-hydroxybisphosphonate conjugated drug (p < 0.001). In contrast, the less labile tedizolid N-phenyl carbamate linked BCA had limited efficacy against MSSA, and MRSA. CFU were recovered from all tedizolid BCA treatments. These results demonstrate the feasibility of BCA eradication of S. aureus biofilm on OLCN bone surfaces and support in vivo drug development of a sitafloxacin BCA.

Highlights

Bone infection, primarily caused by Staphylococcus aureus, remains a scourge in orthopaedic surgery
The incidence of infection following primary total joint replacement (TJR) is low (~1%) [1,2,3], reinfection rates are very high (15–40%) after treatment of an infection related to a joint replacement [4,5,6,7,8], which has led to the established paradigm that S. aureus infection of bone is incurable [9]
While in vivo bromodeoxyuridine labeling studies in mice have demonstrated that orally administered small molecules have access to S. aureus at the leading edge of the colony within the osteocytelacuno canalicular network (OLCN) [17], we have shown that both methicillin-sensitive S. aureus (MSSA) [23] and methicillin-resistant S. aureus (MRSA) [24] OLCN invasion cannot be prevented or eradicated by combined high-dose local and systemic antibiotics, likely due to its well-known adaptive responses that are associated with persister cells and small colony variants (SCVs) [10]

Summary

Introduction

Primarily caused by Staphylococcus aureus, remains a scourge in orthopaedic surgery. The in vivo results showed that a single dose of 10 mg/kg (15.6 mumol/kg) conjugate reduced the colony forming units (CFU) in tissues by 99% and was one order of magnitude more potent than the parent antibiotic ciprofloxacin (30 mg/kg, 90.6 mumol/kg) given in multiple doses Another poorly recognized limitation of conventional antibiotic administration is the effect of local wound drainage on the pharmacodynamics of the therapy. We present evidence of the potent cytolytic activity of sitafloxacin conjugated BP and HBP on MSSA and MRSA static biofilms grown on hydroxyapatite discs in vitro, versus parent antibiotic and tedizolid conjugated BP and HBP

Animal Surgeries and AF647-ZOL Treatment

Findings

Histology and Fluorescent Microscopy