Discovery and characterisation of an antibody that selectively modulates the inhibitory activity of plasminogen activator inhibitor-1.

Plasminogen activator inhibitor-1 (PAI-1) is a serine protease inhibitor (serpin) that regulates fibrinolysis, cell adhesion and cell motility via its interactions with plasminogen activators and vitronectin. PAI-1 has been shown to play a role in a number of diverse pathologies including cardiovascular diseases, obesity and cancer and is therefore an attractive therapeutic target. However the multiple patho-physiological roles of PAI-1, and understanding the relative contributions of these in any one disease setting, make the development of therapeutically relevant molecules challenging. Here we describe the identification and characterisation of fully human antibody MEDI-579, which binds with high affinity and specificity to the active form of human PAI-1. MEDI-579 specifically inhibits serine protease interactions with PAI-1 while conserving vitronectin binding. Crystallographic analysis reveals that this specificity is achieved through direct binding of MEDI-579 Fab to the reactive centre loop (RCL) of PAI-1 and at the same exosite used by both tissue and urokinase plasminogen activators (tPA and uPA). We propose that MEDI-579 acts by directly competing with proteases for RCL binding and as such is able to modulate the interaction of PAI-1 with tPA and uPA in a way not previously described for a human PAI-1 inhibitor.

Disease activity dynamics in rheumatoid arthritis: patients' self-assessment of disease activity via WebApp.

Objectives: The aim was to evaluate patient self-assessment of RA disease activity in terms of Routine Assessment of Patient Index Data (RAPID) scores via a Web-based smartphone application (WebApp). Methods: In this prospective, multicentre study, adult RA patients were examined by a rheumatologist at baseline and after 3 months. Patients were asked to complete WebApp questionnaires weekly. The time course of patient-assessed RAPID3/4 scores and their correlations with rheumatologist-assessed DAS28, as well as Clinical and Simplified Disease Activity Indices (CDAI/SDAI), were evaluated. Results: Eighty patients were included in the analysis (median RA duration, 4.5 years; age, 57 years; 59% female). At baseline, there was a moderate to strong correlation between RAPID3 and DAS28 (r = 0.63), CDAI (r = 0.65) and SDAI (r = 0.61) scores. Similar or stronger correlations were seen at the 3-month follow-up visit (DAS28 r = 0.66, CDAI r = 0.71 and SDAI r = 0.61). Similar correlations were seen between RAPID4 and rheumatologist assessments. Correlations were not influenced by demographics or RA treatment. In the 3-month period, the RAPID3 score changed into a higher severity category than the category at baseline at least once in 47% of patients. When DAS28 scores were predicted from the RAPID3, 11% of patients had an increase of > 1 DAS28 unit during the 3-month observation period. Conclusion: Web-based patient assessments were strongly correlated with rheumatologist assessments of RA activity and showed considerable variation during follow-up. This provides a rationale for further exploration of their use as cost-effective tools to monitor RA activity between outpatient visits and to optimize tight control strategies.

Harnessing phage and ribosome display for antibody optimisation.

Therapeutic antibodies have become a major driving force for the biopharmaceutical industry; therefore, the discovery and development of safe and efficacious antibody leads have become competitive processes. Phage and ribosome display are ideal tools for the generation of such molecules and have already delivered an approved drug as well as a multitude of clinical candidates. Because they are capable of searching billions of antibody variants in tailored combinatorial libraries, they are particularly applicable to potency optimisation. In conjunction with targeted, random or semi-rational mutagenesis strategies, they deliver large panels of potent antibody leads. This review introduces the two technologies, compares them with respect to their use in antibody optimisation and highlights how they can be exploited for the successful and efficient generation of putative drug candidates.

Mutations within the hMLH1 and hPMS2 subunits of the human MutLalpha mismatch repair factor affect its ATPase activity, but not its ability to interact with hMutSalpha.

The MutL family of mismatch repair proteins belongs to the GHKL class of ATPases, which contains also type II topoisomerases, HSP90, and histidine kinases. The nucleotide binding domains of these polypeptides are highly conserved, but this similarity has failed to help us understand the biological role of the ATPase activity of the MutL proteins in mismatch repair. hMutLalpha is a heterodimer of the human MutL homologues hMLH1 and hPMS2, and we decided to exploit its asymmetry to study this function. We now show that although the two subunits contribute differently to the ATPase activity of the heterodimer, hMutLalpha variants in which one subunit was able to bind but not hydrolyze ATP displayed similarly reduced mismatch repair activities in vitro. In contrast, variants in which either subunit was unable to bind the nucleotide were inactive. Mutation of the catalytic sites of both subunits abolished repair without altering the ability of these peptides to interact with one another. Since the binding of the nucleotide in hMutLalpha was not required for the formation of ternary complexes with the mismatch recognition factor hMutSalpha bound to a heteroduplex substrate, we propose that the ATPase activity of hMutLalpha is required downstream from this process.