Ocular Penetration of N-Formimidoyl Thienamycin (MK-787) and Potentiation by Dipeptidase Inhibitor (MK-791)

N-formimidoyl thienamycin (MK-787) is a new /?-lactam with potent activity against both aerobic and anaerobic gram-positive and gram-negative bacteria. Its spectrum and activity suggest it may be useful in treatment of complicated intraocular infections. Its ocular penetration was studied in New Zealand white rabbits immediately before and after the third dose of 40 mg/kg administered intravenously at q6h intervals. Plasma, aqueous humor, and vitreous humor were obtained by direct aspiration, and antibiotic levels were asayed using an agar well diffusion method. MK-787 penetrated uninflamed intraocular fluids, including vitreous humor, although vitreous concentrations achieved (0.1-0.2 Mg/ml) were significantly lower than the mean peak plasma (15 Mg/ml) and aqueous concentrations (7 Mg/ml). Nevertheless, the intraocular levels attained approached or exceeded the MIC 90 and markedly enhanced spectrum of activity against both gram-positive and gram-negative bacteria

Development of PF-06671008, a Highly Potent Anti-P-cadherin/Anti-CD3 Bispecific DART Molecule with Extended Half-Life for the Treatment of Cancer

Bispecific antibodies offer a promising approach for the treatment of cancer but can be challenging to engineer and manufacture. Here we report the development of PF-06671008, an extended-half-life dual-affinity re-targeting (DART®) bispecific molecule against P-cadherin and CD3 that demonstrates antibody-like properties. Using phage display, we identified anti-P-cadherin single chain Fv (scFv) that were subsequently affinity-optimized to picomolar affinity using stringent phage selection strategies, resulting in low picomolar potency in cytotoxic T lymphocyte (CTL) killing assays in the DART format. The crystal structure of this disulfide-constrained diabody shows that it forms a novel compact structure with the two antigen binding sites separated from each other by approximately 30 Å and facing approximately 90° apart. We show here that introduction of the human Fc domain in PF-06671008 has produced a molecule with an extended half-life (-4.4 days in human FcRn knock-in mice), high stability (Tm1 > 68 °C), high expression (>1 g/L), and robust purification properties (highly pure heterodimer), all with minimal impact on potency. Finally, we demonstrate in vivo anti-tumor efficacy in a human colorectal/human peripheral blood mononuclear cell (PBMC) co-mix xenograft mouse model. These results suggest PF-06671008 is a promising new bispecific for the treatment of patients with solid tumors expressing P-cadherin