PDF inhibitors: an emerging class of antibacterial drugs.

The metalloenzyme peptide deformylase (PDF) represents one of the most promising bacterial targets in the search for novel mode of action antibiotics that lack cross-resistance to existing drugs. Initial research and clinical development has focused on anti-pneumococcal applications. During optimization, peptide analogs were developed containing either a hydroxamate or formyl-hydroxylamine as metal interacting group, yielding inhibitors with in vitro activity against a broad spectrum of organisms. Preclinical studies revealed potent antibacterial activity in vivo that is paired with good pharmacokinetic properties and excellent tolerability in different species. BB-83698, a potent PDF inhibitor with i.v. and oral efficacy in preclinical animal models, represents the first class-representative compound evaluated in man. The inhibitor was administered by i.v. infusion and was shown to exhibit generally dose-proportional pharmacokinetics. It was well tolerated up to doses providing predicted therapeutic exposures. These human results, combined with the preclinical information, clearly support the potential of PDF inhibitors for development as a novel class of antibacterial therapeutics.

Oral anti-pneumococcal activity and pharmacokinetic profiling of a novel peptide deformylase inhibitor.

OBJECTIVE: BB-81384, a novel peptide deformylase (PDF) inhibitor, was characterized in terms of enzyme inhibition profile, antibacterial activity, rodent pharmacokinetics and oral efficacy in murine infection models. METHODS: MICs were determined by standard NCCLS broth microdilution. Selectivity of metalloenzyme inhibition was determined with a limited panel of enzymes via standard biochemical assays. Profiling of the pharmacokinetics and select tissue disposition in mice was determined and compared with that of the macrolide, azithromycin. In vivo murine efficacy studies using Streptococcus pneumoniae were conducted using a peritonitis model, as well as lung and thigh burden models of infection. RESULTS: BB-81384 selectively inhibited PDF with an IC(50) approximately 10 nM and with MICs < 0.5 mg/L against most S. pneumoniae pathogens. Pharmacokinetic analysis revealed good oral bioavailability and moderate clearance and volume of distribution. BB-81384 partitioning to lung tissue was similar in terms of magnitude and kinetics to that of the plasma compartment. Single-administration oral efficacy in a mouse peritonitis model was evident with an ED(50) of 30 mg/kg. BB-81384 reduced the bacterial load by approximately 5 and 3 log units in organ-burden models of lung and thigh infection, respectively. CONCLUSION: BB-81384, a novel PDF inhibitor with good activity against S. pneumoniae in vitro, was the first compound of this class to be profiled for oral pharmacokinetics and tissue disposition and to demonstrate oral anti-pneumococcal efficacy in mice.

Detection of a common mutation in factor V gene responsible for resistance to activate protein C causing predisposition to thrombosis.

Hereditary predisposition to thrombosis due to activated protein C resistance (APCR) has been attributed to a missense mutation in the factor V gene at nucleotide 1691 (G to A), causing replacement of arginine at codon 506 with glutamine. Using an RFLP-PCR assay to detect this mutation, we measured a prevalence of 3.3% in healthy Caucasians and 1.25% in healthy African-Americans. In addition, we evaluated a total of 90 consecutive specimens submitted to the coagulation laboratory at the Medical College of Virginia for the presence of this mutation. We compared our results for 78 of these specimens with the values measured by a modified partial thromboplastin assay, the COATEST. Twelve of the 90 samples could not be tested using the COATEST because the patients were undergoing anticoagulant therapy. One of the latter 12 specimens was positive by the RFLP-PCR test. Using the genetic test as the definitive assay and the cutoff value established for distinguishing between normal and abnormal results by the COATEST, the COATEST had a sensitivity of 50% and specificity of 93% for the detection of factor V mutation. Analysis of the 90 samples stratified by ethnic groups revealed a frequency of mutation of 13.3% for Caucasians and 6.88% for African-Americans, although with the present sample size, the difference was not statistically significant. Although the COATEST is technically simpler to perform than the genetic test for diagnosing the presence of the factor V mutation, its use for this purpose is limited due to low sensitivity. Thus where this disorder is clinically suspected, submission of the specimen directly for genetic testing by RFLP-PCR or equivalent assay should be considered.