Stereocontrolled Synthesis of Arylomycin-Based Gram-Negative Antibiotic GDC-5338

We report herein an efficient, stereocontrolled, and chromatography-free synthesis of the novel broad spectrum antibiotic GDC-5338. The route features the construction of a functionalized tripeptide backbone, a high-yielding macrocyclization via a Pd-catalyzed Suzuki-Miyaura reaction, and the late-stage elaboration of key amide bonds with minimal stereochemical erosion. Through extensive reaction development and analytical understanding, these key advancements allowed the preparation of GDC-5338 in 17 steps, 15% overall yield, >99 A % HPLC, and >99:1 dr.

Convergent Synthesis of PI3K Inhibitor GDC-0908 Featuring Palladium-Catalyzed Direct C-H Arylation toward Dihydrobenzothienooxepines

A practical convergent synthesis of PI3K inhibitor GDC-0908 (1) is described. The process features a dihydrobenzothienooxepine formation via palladium-catalyzed intramolecular direct C-H arylation and a Negishi coupling to construct the key C-C bonds. We further developed a general synthesis of dihydrobenzothienooxepines in good to excellent yields via palladium-catalyzed intramolecular direct C-H arylation, which tolerates both electronically and sterically diverse substituents on the phenyl ring.

Macrolactamization Approaches to Arylomycin Antibiotics Core

Two practical entries to arylomycin antibiotics core structures are investigated. In route A, the activation of l-Hpg for the key macrolactamization step is achieved in 89% yield in the presence of unprotected phenol and amine functionalities. Alternatively, a propanephosphonic acid anhydride (T3P)-promoted coupling between thel-Tyr and l-Ala moieties in route B led to a facile macrolactamization in 68% yield with a marked reduction in competing oligomerization.

Potent and selective Bruton's tyrosine kinase inhibitors: discovery of GDC-0834

SAR studies focused on improving the pharmacokinetic (PK) properties of the previously reported potent and selective Btk inhibitor CGI-1746 (1) resulted in the clinical candidate GDC-0834 (2), which retained the potency and selectivity of CGI-1746, but with much improved PK in preclinical animal models. Structure based design efforts drove this work as modifications to 1 were investigated at both the solvent exposed region as well as 'H3 binding pocket'. However, in vitro metabolic evaluation of 2 revealed a non CYP-mediated metabolic process that was more prevalent in human than preclinical species (mouse, rat, dog, cyno), leading to a high-level of uncertainly in predicting human pharmacokinetics. Due to its promising potency, selectivity, and preclinical efficacy, a single dose IND was filed and 2 was taken in to a single dose phase I trial in healthy volunteers to quickly evaluate the human pharmacokinetics. In human, 2 was found to be highly labile at the exo-cyclic amide bond that links the tetrahydrobenzothiophene moiety to the central aniline ring, resulting in insufficient parent drug exposure. This information informed the back-up program and discovery of improved inhibitors.

Significant species difference in amide hydrolysis of GDC-0834, a novel potent and selective Bruton's tyrosine kinase inhibitor

(R)-N-(3-(6-(4-(1,4-dimethyl-3-oxopiperazin-2-yl)phenylamino)-4-methyl-5-oxo-4,5-dihydropyrazin-2-yl)-2-methylphenyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxamide (GDC-0834) is a potent and selective inhibitor of Bruton's tyrosine kinase (BTK), investigated as a potential treatment for rheumatoid arthritis. In vitro metabolite identification studies in hepatocytes revealed predominant formation of an inactive metabolite (M1) via amide hydrolysis in human. The formation of M1 appeared to be NADPH-independent in human liver microsomes. M1 was found in only minor to moderate quantities in plasma from preclinical species dosed with GDC-0834. Human clearance predictions using various methodologies resulted in estimates ranging from low to high. In addition, GDC-0834 exhibited low clearance in PXB chimeric mice with humanized liver. Uncertainty in human pharmacokinetic prediction and high interest in a BTK inhibitor for clinical evaluation prompted an investigational new drug strategy, in which GDC-0834 was rapidly advanced to a single-dose human clinical trial. GDC-0834 plasma concentrations in humans were below the limit of quantitation (<1 ng/ml) in most samples from the cohorts dosed orally at 35 and 105 mg. In contrast, substantial plasma concentrations of M1 were observed. In human plasma and urine, only M1 and its sequential metabolites were identified. The formation kinetics of M1 was evaluated in rat, dog, monkey, and human liver microsomes in the absence of NADPH. The maximum rate of M1 formation (V(max)) was substantially higher in human compared with that in other species. In contrast, the Michaelis-Menten constant (K(m)) was comparable among species. Intrinsic clearance (V(max)/K(m)) of GDC-0834 from M1 formation in human was 23- to 169-fold higher than observed in rat, dog, and monkey.

Essential role of phosphoinositide 3-kinase delta in neutrophil directional movement

Neutrophil chemotaxis is a critical component of the innate immune response. Neutrophils can sense an extremely shallow gradient of chemoattractants and produce relatively robust chemotactic behavior. This directional migration requires cell polarization with actin polymerization occurring predominantly in the leading edge. Synthesis of phosphatidylinositol (3,4,5) trisphosphate (PIP3) by phosphoinositide 3-kinase (PI3K) contributes to asymmetric F-actin synthesis and cell polarization during neutrophil chemotaxis. To determine the contribution of the hemopoietic cell-restricted PI3K delta in neutrophil chemotaxis, we have developed a potent and selective PI3K delta inhibitor, IC87114. IC87114 inhibited polarized morphology of neutrophils, fMLP-stimulated PIP3 production and chemotaxis. Tracking analysis of IC87114-treated neutrophils indicated that PI3K delta activity was required for the directional component of chemotaxis, but not for random movement. Inhibition of PI3K delta, however, did not block F-actin synthesis or neutrophil adhesion. These results demonstrate that PI3K delta can play a selective role in the amplification of PIP3 levels that lead to neutrophil polarization and directional migration.

The novel glycolipid RC-552 attenuates myocardial stunning and reduces infarct size in dogs

The novel glycolipid RC-552 shares common structural features with the natural products lipid A and the previously described cardioprotectant monophosphoryl lipid A. RC-552 administered to dogs as a bolus intravenous dose (35-70 microg/kg) either 24 h or 10 min prior to 60 min of regional myocardial ischemia and 3 h of reperfusion significantly (P<0.05 v control) reduced infarct size (IS) as assessed by triphenyltetrazolium staining from 27.0+/-2.3% of the area-at-risk (AAR) to 13.3+/-2.2% and 15.0+/-3.0%, respectively. Administration of the non-specific inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine (30 mg/kg, subcutaneously) 1 h prior to ischemia blocked the ability of RC-552 (35 microg/kg, 24 h pretreatment) to reduce infarct size. Intravenous pretreatment with RC-552 (35 microg/kg) either 24 h or 10 min prior to five 5 min repetitive cycles of ischemia and reperfusion significantly improved regional myocardial segment shortening (percentage of control) at all time points during 2 h of reperfusion in dogs. These effects of RC-552 in either cardiac injury model occurred independent of differences in AAR, transmural blood flow during ischemia or hemodynamics throughout the experiment. In contrast with monophosphoryl lipid A (MLA), which has also been reported to be cardioprotective at similar doses in dogs, RC-552 was approximately 100 times less prone to cause fever in the USP rabbit pyrogen test. Likewise, RC-552 did not induce secretion of the proinflammatory cytokines TNF, IL-6 or IL-8 from THP-1 cells or alter the expression of adhesion molecules on human neutrophils at concentrations up to 10 microg/ml. MLA was active in these systems at concentrations in the range 0.1-1.0 microg/ml. In conclusion, RC-552 reduces myocardial infarct size and stunning in dogs in the absence of residual immunomodulatory activity.

3-O-Desacyl monophosphoryl lipid A derivatives: synthesis and immunostimulant activities

The synthesis of a series of novel analogues of lipid A, the active principle of lipopolysaccharide, is reported. In these compounds, the 1-O-phosphono and (R)-3-hydroxytetradecanoyl moieties of native Salmonella minnesota R595 lipid A have been replaced with hydrogen and the length of the normal fatty acyl residues has been systematically varied. Normal fatty acid chain length in the 3-O-desacyl monophosphoryl lipid A (MLA) series is shown to be a critical determinant of iNOS gene expression in activated mouse macrophages and the induction of proinflammatory cytokines in human peripheral monocytes. Examination of pyrogenicity in rabbits and lethal toxicity in D-galactosamine-treated mice shows that toxic effects in the MLA series can be ameliorated by modifying fatty acid chain length. When used as an adjuvant for tetanus toxoid vaccines, certain MLA derivatives enhance the production of tetanus toxoid-specific antibodies in mice.

Synthesis and biological evaluation of a new class of vaccine adjuvants: aminoalkyl glucosaminide 4-phosphates (AGPs)

A novel series of acylated omega-aminoalkyl 2-amino-2-deoxy-4-phosphono-beta-D-glucopyranosides (aminoalkyl glucosaminide 4-phosphates) was synthesized and screened for immunostimulant activity. Several of these compounds enhance the production of tetanus toxoid-specific antibodies in mice and augment vaccine-induced cytotoxic T cells against EG.7-ova target cells.