Discovery of a High Affinity, Orally Bioavailable Macrocyclic FXIa Inhibitor with Antithrombotic Activity in Preclinical Species.

Oral factor XIa (FXIa) inhibitors may provide a promising new antithrombotic therapy with an improved benefit to bleeding risk profile over existing antithrombotic agents. Herein, we report application of a previously disclosed cyclic carbamate P1 linker which provided improved oral bioavailability in the imidazole-based 13-membered macrocycle to the 12-membered macrocycle. This resulted in identification of compound 4 with desired FXIa inhibitory potency and good oral bioavailability but high in vivo clearance. Further structure-activity relationship (SAR) studies of heterocyclic core modifications to replace the imidazole core as well as various linkers to the P1 group led to the discovery of compound 6f, a potent FXIa inhibitor with selectivity against most of the relevant serine proteases. Compound 6f also demonstrated excellent pharmacokinetics (PK) profile (high oral bioavailability and low clearance) in multiple preclinical species. Compound 6f achieved robust antithrombotic efficacy in a rabbit efficacy model at doses which preserved hemostasis.

Management of anti-Jka alloimmunization.

OBJECTIVE: To determine whether prenatal management using guidelines established for anti-D is applicable to anti-Jka. STUDY DESIGN: A computerized database containing the records of all alloimmunized pregnancies at The Ohio State University Medical Center with due dates from 1959 to 2008 was used to identify pregnancies affected only by anti-Jka. Only cases with evidence that the newborn was Jka antigen positive were included. RESULTS: Twenty affected pregnancies met inclusion criteria. Of those, 16 pregnancies required monitoring with serum titers only and 4 were followed with more diagnostic tests as recommended during that time period. One pregnancy with the highest titer of 32 and elevated middle cerebral artery peak systolic velocity (MCA PSV) required 4 intrauterine transfusions for fetal anemia. Another pregnancy with a titer of 32 had an infant who required phototherapy for hemolytic disease of the fetus/newborn (HDFN), with a hemoglobin value of 15.9 g/dL. None of the other 18 infants required any therapy for HDFN. CONCLUSION: Our case series identified severe disease in 1 of 20 pregnancies from anti-Jka using maternal antibody titer and MCA PSV. Criteria used for monitoring RhD alloimmunization were effective in detecting severe HDFN resulting from to anti-Jka.

Understanding and modulating cyclin-dependent kinase inhibitor specificity: molecular modeling and biochemical evaluation of pyrazolopyrimidinones as CDK2/cyclin A and CDK4/cyclin D1 inhibitors.

Cyclin-dependent kinases (CDKs) play a key role in regulating the cell cycle. The cyclins, their activating agents, and endogenous CDK inhibitors are frequently mutated in human cancers, making CDKs interesting targets for cancer chemotherapy. Our aim is the discovery of selective CDK4/cyclin D1 inhibitors. An ATP-competitive pyrazolopyrimidinone CDK inhibitor was identified by HTS and docked into a CDK4 homology model. The resulting binding model was consistent with available SAR and was validated by a subsequent CDK2/inhibitor crystal structure. An iterative cycle of chemistry and modeling led to a 70-fold improvement in potency. Small substituent changes resulted in large CDK4/CDK2 selectivity changes. The modeling revealed that selectivity is largely due to hydrogen-bonded interactions with only two kinase residues. This demonstrates that small differences between enzymes can efficiently be exploited in the design of selective inhibitors.