Phosphodiesterase 9 inhibition prolongs the antiparkinsonian action of l-DOPA in parkinsonian non-human primates.

Phosphodiesterase 9 (PDE9) degrades selectively the second messenger cGMP, which is an important molecule of dopamine signaling pathways in striatal projection neurons (SPNs). In this study, we assessed the effects of a selective PDE9 inhibitor (PDE9i) in the primate model of Parkinson's disease (PD). Six macaques with advanced parkinsonism were used in the study. PDE9i was administered as monotherapy and co-administration with l-DOPA at two predetermined doses (suboptimal and threshold s.c. doses of l-Dopa methyl ester plus benserazide) using a controlled blinded protocol to assess motor disability, l-DOPA -induced dyskinesias (LID), and other neurologic drug effects. While PDE9i was ineffective as monotherapy, 2.5 and 5 mg/kg (s.c.) of PDE9i significantly potentiated the antiparkinsonian effects of l-DOPA with a clear prolongation of the "on" state (p < 0.01) induced by either the suboptimal or threshold l-DOPA dose. Co-administration of PDE9i had no interaction with l-DOPA pharmacokinetics. PDE9i did not affect the intensity of LID. These results indicate that cGMP upregulation interacts with dopamine signaling to enhance the l-DOPA reversal of parkinsonian motor disability. Therefore, striatal PDE9 inhibition may be further explored as a strategy to improve motor responses to l-DOPA in PD.

Discovery of Novel, Potent Inhibitors of Hydroxy Acid Oxidase 1 (HAO1) Using DNA-Encoded Chemical Library Screening.

Inhibition of hydroxy acid oxidase 1 (HAO1) is a strategy to mitigate the accumulation of toxic oxalate that results from reduced activity of alanine-glyoxylate aminotransferase (AGXT) in primary hyperoxaluria 1 (PH1) patients. DNA-Encoded Chemical Library (DECL) screening provided two novel chemical series of potent HAO1 inhibitors, represented by compounds 3-6. Compound 5 was further optimized via various structure-activity relationship (SAR) exploration methods to 29, a compound with improved potency and absorption, distribution, metabolism, and excretion (ADME)/pharmacokinetic (PK) properties. Since carboxylic acid-containing compounds are often poorly permeable and have potential active glucuronide metabolites, we undertook a brief, initial exploration of acid replacements with the aim of identifying non-acid-containing HAO1 inhibitors. Structure-based drug design initiated with Compound 5 led to the identification of a nonacid inhibitor of HAO1, 31, which has weaker potency and increased permeability.

Discovery of 2,4-1H-Imidazole Carboxamides as Potent and Selective TAK1 Inhibitors.

Herein we report the discovery of 2,4-1H-imidazole carboxamides as novel, biochemically potent, and kinome selective inhibitors of transforming growth factor ß-activated kinase 1 (TAK1). The target was subjected to a DNA-encoded chemical library (DECL) screen. After hit analysis a cluster of compounds was identified, which was based on a central pyrrole-2,4-1H-dicarboxamide scaffold, showing remarkable kinome selectivity. A scaffold-hop to the corresponding imidazole resulted in increased biochemical potency. Next, X-ray crystallography revealed a distinct binding mode compared to other TAK1 inhibitors. A benzylamide was found in a perpendicular orientation with respect to the core hinge-binding imidazole. Additionally, an unusual amide flip was observed in the kinase hinge region. Using structure-based drug design (SBDD), key substitutions at the pyrrolidine amide and the glycine resulted in a significant increase in biochemical potency.

Bispecific Estrogen Receptor α Degraders Incorporating Novel Binders Identified Using DNA-Encoded Chemical Library Screening.

Bispecific degraders (PROTACs) of ERα are expected to be advantageous over current inhibitors of ERα signaling (aromatase inhibitors/SERMs/SERDs) used to treat ER+ breast cancer. Information from DNA-encoded chemical library (DECL) screening provides a method to identify novel PROTAC binding features as the linker positioning, and binding elements are determined directly from the screen. After screening ∼120 billion DNA-encoded molecules with ERα WT and 3 gain-of-function (GOF) mutants, with and without estradiol to identify features that enrich ERα competitively, the off-DNA synthesized small molecule exemplar 7 exhibited nanomolar ERα binding, antagonism, and degradation. Click chemistry synthesis on an alkyne E3 ligase engagers panel and an azide variant of 7 rapidly generated bispecific nanomolar degraders of ERα, with PROTACs 18 and 21 inhibiting ER+ MCF7 tumor growth in a mouse xenograft model of breast cancer. This study validates this approach toward identifying novel bispecific degrader leads from DECL screening with minimal optimization.

Identification of 5-(1-Methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl)thiophene-2-Carboxamides as Novel and Selective Monoamine Oxidase B Inhibitors Used to Improve Memory and Cognition.

Initial work in Drosophila and mice demonstrated that the transcription factor cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) is a master control gene for memory formation. The relationship between CREB and memory has also been found to be true in other species, including aplysia and rats. It is thus well-established that CREB activation plays a central role in memory enhancement and that CREB is activated during memory formation. On the basis of these findings, a phenotypic high-throughput screening campaign utilizing a CRE-luciferase (CRE-Luci) SK-N-MC cell line was performed to identify compounds that enhance transcriptional activation of the CRE promoter with a suboptimal dose of forskolin. A number of small-molecule hits of unknown mechanisms of action were identified in the screening campaign, including HT-0411. Follow-up studies suggested that the CREB activation by HT-0411 is attributed to its specific and selective inhibition of monoamine oxidase B (MAO-B). Further, HT-0411 was shown to improve 24 h memory in rodents in a contextual fear conditioning model. This report describes the lead optimization of a series of 5-(1-methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl) thiophene-2-carboxamides that were identified as novel, potent, and selective inhibitors of MAO-B. Extensive SAR studies and in vivo behavioral evaluations of this and other related analogue series identified a number of potential clinical development candidates; ultimately, compound 8f was identified as a candidate molecule with high selectivity toward MAO-B (29-56 nM) over MAO-A (19% inhibition at a screening concentration of 50 µM), an excellent profile against a panel of other enzymes and receptors, good pharmacokinetic properties in rodents and dogs, and efficacy in multiple rodent memory models.

Biological mechanisms of action of novel C-10 non-acetal trioxane dimers in prostate cancer cell lines.

The mechanisms of action of three C-10 non-acetal trioxane dimers (TDs) were examined in human (LNCaP) and mouse (TRAMP-C1A and -C2H) prostate cancer cell lines. 1 (AJM3/23), 2 (GHP-TM-III-07w), and 3 (GHP-KB-06) inhibited cell growth with 3 being the most potent in C1A (GI50 = 18.0 nM), C2H (GI50 = 17.0 nM), and LNCaP (GI50 = 17.9 nM) cells. In comparison to a standard cytotoxic agent such as doxorubicin (GI50 = 45.3 nM), 3 (GI50 = 17.9 nM) inhibited LNCaP cell growth more potently. TDs induced G0/G1 cell cycle arrest in LNCaP cells and decreased cells in the S phase. These changes correlated with modulation of G1 phase cell cycle proteins including decreased cyclin D1, cyclin E, and cdk2 and increased p21waf1 and p27Kip1. TDs also promoted apoptosis in LNCaP cells with increased expression of proapoptotic bax. These results demonstrate that TDs are potentially useful agents that warrant further preclinical development for treatment of prostate cancer.

Anticancer and antimalarial efficacy and safety of artemisinin-derived trioxane dimers in rodents.

In only four chemical steps from naturally occurring artemisinin (1), trioxane dimers 6 and 7 were prepared on a multigram scale in overall 32-44% yields. In mice, both isonicotinate N-oxide dimer 6 and isobutyric acid dimer 7 were considerably more antimalarially efficacious than clinically used sodium artesunate (2) via both oral and intravenous administration. In the transgenic adenocarcinoma of mouse prostate model, some of the trioxane dimers had potent anticancer activity.

Orally active, antimalarial, anticancer, artemisinin-derived trioxane dimers with high stability and efficacy.

In only two steps and in 70% overall yield, naturally occurring trioxane artemisinin (1) was converted on a gram scale into C-10-carba trioxane dimer 3. This new, very stable dimer was then transformed easily in one additional step into four different dimers 4-7. Alcohol and diol dimers 4 and 5 and ketone dimer 7 are 10 times more antimalarially potent in vitro than artemisinin (1), and alcohol and diol dimers 4 and 5 are strongly growth inhibitory but not cytotoxic toward several human cancer cell lines. Water-soluble carboxylic acid derivatives 8aand 9 were easily prepared in one additional step from dimers 4 and 5. Carboxylic acid dimers 8a and 9 are thermally stable even at 60 degrees C for 24 h, are more orally efficacious as antimalarials in rodents than either artelinic acid or sodium artesunate, and are strongly inhibitory but not cytotoxic toward several human cancer cell lines.