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Human activated protein C (APC) is an antithrombotic, antiinflammatory serine protease that plays a central role in vascular homeostasis, and activated recombinant protein C, drotrecogin alfa (activated), has been shown to reduce mortality in patients with severe sepsis. Similar to other serine proteases, functional APC levels are regulated by the serine protease inhibitor family of proteins including ␣1-antitrypsin and protein C inhibitor. Using APC-substrate modeling, we designed and produced a number of derivatives with the goal of altering the proteolytic specificity of APC such that the variants exhibited resistance to inactivation by protein C inhibitor and ␣1-antitrypsin yet maintained their primary anticoagulant activity. Substitutions at Leu-194 were of particular interest, because they exhibited 4-to 6-fold reductions in the rate of inactivation in human plasma and substantially increased pharmacokinetic profiles compared with wild-type APC. This was achieved with minimal impairment of the anticoagulant͞ antithrombotic activity of APC. These data demonstrate the ability to selectively modulate substrate specificity and subsequently affect in vivo performance and suggest therapeutic opportunities for the use of protein C derivatives in disease states with elevated serine protease inhibitor levels.

We achieved equal or slightly better glucose control, as reflected by mean amplitude of glucose excursion, with insulin lispro given much closer to meal time than that achieved with regular insulin. As a result of these findings, we propose that a rapidly absorbed analogue of insulin is capable of achieving better control of postprandial glucose at a more convenient injection time.

Insulin lispro is an insulin analog in which the primary sequence has been altered by the inversion of amino acids B28 and B29. To date, it has not been possible to specifically measure insulin lispro in the presence of endogenous insulin because of the high degree of homology between these peptides. However, the specific determination of insulin lispro offers advantages over quantifying total concentrations of immunoreactive insulin. We therefore immunized guinea pigs and screened for antibodies with increased affinity and selectivity for insulin lispro. We prepared a monospecific antiserum by a novel immunoadsorption strategy using despentapeptide insulin. The antiserum was used to develop a competitive RIA for insulin lispro. The RIA has a low limit of quantification (17.2 pmol/L); has no interference from insulin, proinsulin, or C-peptide; and has interassay CVs of 2.6–13.4%. The new RIA is useful for measuring serum concentrations of insulin lispro.

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