The crystal structures of TrkA and TrkB suggest key regions for achieving selective inhibition.

The Trk family of neurotrophin receptors, which includes the three highly homologous proteins TrkA, TrkB and TrkC, is strongly associated with central and peripheral nervous system processes. Trk proteins are also of interest in oncology, since Trk activation has been observed in several cancer types. While Trk kinases are attractive oncology targets, selectivity might be more of an issue than for other kinases due to potential CNS side effects if several Trk kinases are simultaneously targeted. In order to address this issue, we present here the first structures of human TrkA and TrkB kinase domains and three complexes between TrkB and Trk inhibitors. These structures reveal different conformations of the kinase domain and suggest new regions of selectivity among the Trk family.

Design of yeast-secreted albumin derivatives for human therapy: biological and antiviral properties of a serum albumin-CD4 genetic conjugate.

Due to its remarkably long half-life, together with its wide in vivo distribution and its lack of enzymatic or immunological functions, human serum albumin (HSA) represents an optimal carrier for therapeutic peptides/proteins aimed at interacting with cellular or molecular components of the vascular and interstitial compartments. As an example, we designed a genetically engineered HSA-CD4 hybrid aimed at specifically blocking the entry of the human immunodeficiency virus into CD4+ cells. In contrast with CD4, HSA-CD4 is correctly processed and efficiently secreted by Kluyveromyces yeasts. In addition, its CD4 moiety exhibits binding and antiviral in vitro properties similar to those of soluble CD4. Finally, the elimination half-life of HSA-CD4 in a rabbit experimental model is comparable to that of control HSA and 140-fold higher than that of soluble CD4. These results indicate that the genetic fusion of bioactive peptides to HSA is a plausible approach toward the design and recovery of secreted therapeutic HSA derivatives with appropriate pharmacokinetic properties.