Paolo Pevarello

Identification of N,1,4,4-Tetramethyl-8-{[4-(4-Methylpiperazin-1-Yl)Phenyl]Amino}-4,5-Dihydro-1H-Pyrazolo[4,3-H]Quinazoline-3-Carboxamide (Pha-848125), a Potent, Orally Available Cyclin Dependent Kinase Inhibitor.

The discovery of a novel class of inhibitors of cyclin dependent kinases (CDKs) is described. Starting from compound 1, showing good potency as inhibitor of CDKs but being poorly selective against a panel of serine-threonine and tyrosine kinases, new analogues were synthesized. Enhancement in selectivity, antiproliferative activity against A2780 human ovarian carcinoma cells, and optimization of the physical properties and pharmacokinetic profile led to the identification of highly potent and orally available compounds. Compound 28 (PHA-848125), which in the preclinical xenograft A2780 human ovarian carcinoma model showed good efficacy and was well tolerated upon repeated daily treatments, was identified as a drug candidate for further development. Compound 28 is currently undergoing phase I and phase II clinical trials.

PNU-151774E protects against kainate-induced status epilepticus and hippocampal lesions in the rat.

Kainic acid-induced multifocal status epilepticus in the rat is a model of medically intractable complex partial seizures and neurotoxicity. The exact mechanisms of kainic acid epileptogenic and neurotoxic effects are unknown, but enhanced glutamate release seems to be an important factor. PNU-151774E ((S)-(+)-2-(4-(3-fluorobenzyloxy) benzylamino) propanamide, methanesulfonate) is a broad-spectrum new anticonvulsant with Na+ channel-blocking and glutamate release inhibiting properties. We have examined the effect of pretreatment with this compound on both seizure activity and hippocampal neuronal damage induced by systemic injection of kainic acid in rats. Lamotrigine, a recently developed anticonvulsant with similar glutamate release inhibitory properties, was tested for comparison, together with diazepam as reference standard, on the basis of its anticonvulsant and neuroprotectant properties in this animal model. PNU-151774E, lamotrigine (10, 30 mg/kg; i.p.) and diazepam (20 mg/kg; i.p.) were administered 15 min before kainic acid (10 mg/kg; i.p.). In the vehicle-treated group, kainic acid injection caused status epilepticus in 86% of animals. Hippocampal neuronal cell loss was 66% in the CA4 hippocampal area at 7 days after kainic acid administration. Diazepam inhibited both seizures and neurotoxicity. Lamotrigine reduced hippocampal neuronal cell loss at both doses, even when it did not protect from seizures, although it showed a trend toward protection. On the other hand PNU-151774E protected from both hippocampal neurodegeneration and status epilepticus. Thus, these data support the concept that seizure prevention and neuroprotection might not be tightly coupled. Glutamate release inhibition may play a major role in neuroprotection, but an additional mechanism(s) of action might be relevant for the anticonvulsant activity of PNU-151774E in this model.

Pim 1 kinase inhibitor ETP-45299 suppresses cellular proliferation and synergizes with PI3K inhibition

The serine/threonine Pim 1 kinase is an oncogene whose expression is deregulated in several human cancers. Overexpression of Pim 1 facilitates cell cycle progression and suppresses apoptosis. Hence pharmacologic inhibitors of Pim 1 are of therapeutic interest for cancer. ETP-45299 is a potent and selective inhibitor of Pim 1 that inhibits the phosphorylation of Bad and 4EBP1 in cells and suppresses the proliferation of several non-solid and solid human tumor cell lines. The combination of the PI3K inhibitor GDC-0941 with ETP-45299 was strongly synergistic in MV-4-11 AML cells, indicating that the combination of selective Pim kinase inhibitors and PI3K inhibitor could have clinical benefit.

Structure-based approaches to improve selectivity: CDK2-GSK3beta binding site analysis.

An evaluation and comparison of two different approaches, GRID/CPCA and GRIND/CPCA (CPCA = consensus principal component analysis; GRIND = GRid-INdependent Descriptors), suitable for visualizing the structural differences between related proteins is presented. Ten crystal structures of CDK2/cyclin A and GSK3beta solved in-house with different inhibitors were compared with the aim of highlighting regions that could be potential sites for gaining selectivity for CDK2 versus GSK3beta. The analyses pointed out remarkable differences in the backs of the CDK2-GSK3beta ATP binding pockets that guided the optimization toward a selective benzodipyrazole CDK2 inhibitor. The gain in selectivity can be associated with the two main differences in the ATP pocket between the enzymes. Phe80 of CDK2, the so-called gatekeeper residue often exploited for the design of kinase selective ligands, is replaced by a leucine in GSK3beta, and Ala144 is replaced by a cysteine. As a consequence of these mutations, CDK2 has a less elongated and less flat buried region at the back of the ATP pocket.

Identification of potent pyrazolo[4,3-h]quinazoline-3-carboxamides as multi-cyclin-dependent kinase inhibitors.

Abnormal proliferation mediated by disruption of the mechanisms that keep the cell cycle under control is a hallmark of virtually all cancer cells. Compounds targeting complexes between cyclin-dependent kinases (CDKs) and cyclins (Cy) and inhibiting their activity are regarded as promising antitumor agents to complement the existing therapies. An expansion of pyrazolo[4,3-h]quinazoline chemical class oriented to the development of three points of variability was undertaken leading to a series of compounds able to inhibit CDKs both in vitro and in vivo. Starting from the CDK selective but poorly soluble hit compound 1, we succeeded in obtaining several compounds showing enhanced inhibitory activity both on CDKs and on tumor cells and displaying improved physical properties and pharmacokinetic behavior. Our study led to the identification of compound 59 as a highly potent, orally bioavailable CDK inhibitor that exhibited significant in vivo efficacy on the A2780 ovarian carcinoma xenograft model. The demonstrated mechanisms of action of compound 59 on cancer cell lines and its ability to inhibit tumor growth in vivo render this compound very interesting as potential antineoplastic agent.

Optimization of 6,6-Dimethyl Pyrrolo[3,4-C]Pyrazoles: Identification of Pha-793887, a Potent Cdk Inhibitor Suitable for Intravenous Dosing.

We have recently reported CDK inhibitors based on the 6-substituted pyrrolo[3,4-c]pyrazole core structure. Improvement of inhibitory potency against multiple CDKs, antiproliferative activity against cancer cell lines and optimization of the physico-chemical properties led to the identification of highly potent compounds. Compound 31 (PHA-793887) showed good efficacy in the human ovarian A2780, colon HCT-116 and pancreatic BX-PC3 carcinoma xenograft models and was well tolerated upon daily treatments by iv administration. It was identified as a drug candidate for clinical evaluation in patients with solid tumors.

Derivatives of kynurenine as inhibitors of rat brain kynurenine aminotransferase

Abstract The structural requirements of the catalytic site of kynurenine aminotransferase (KAT), the enzyme responsible for the conversion of l -kynurenine (KYN) to kynurenic acid (KYNA), were examined using analogs and derivatives of KYN. KYNA production from KYN was monitored in rat brain homogenates and brain tissue slices. Modification of KYNs acylalanine side chain or its ring amino group resulted in compounds which did not substantially affect KYNA synthesis. Ring chlorination in positions 3, 4, 5 and 6 yielded KYN analogs which interfered with KYNA production. l -5-Cl-KYN was the most active of the chlorinated kynurenines, and one of the most potent of several other 5-substituted kynurenines. l -5-Cl-KYN was an excellent substrate of KAT, yielding 6-Cl-KYNA. Finally, in kinetic studies, l -5-Cl-KYN ( K i = 5.4 μM) was found to have an approximately five times higher affinity to the enzyme than the natural substrate KYN ( K m = 28 μM).

6-Substituted Pyrrolo[3,4-c]pyrazoles: An Improved Class of CDK2 Inhibitors

We have recently reported a new class of CDK2/cyclin A inhibitors based on a bicyclic tetrahydropyrrolo[3,4‐c]pyrazole scaffold. The introduction of small alkyl or cycloalkyl groups in position 6 of this scaffold allowed variation at the other two diversity points. Conventional and polymer‐assisted solution phase chemistry provided a way of generating compounds with improved biochemical and cellular activity. Optimization of the physical properties and pharmacokinetic profile led to a compound which exhibited good efficacy in vivo on A2780 human ovarian carcinoma.

4-Phenyl-4-oxo-butanoic acid derivatives inhibitors of kynurenine 3-hydroxylase

Kynurenine 3-hydroxylase (KYN 3-OHase) is a key enzyme in the kynurenine pathway of tryptophan degradation and its inhibition may be an effective mechanism for counteracting neuronal excitotoxic damage. We present here a new class of inhibitors derived from a structure-activity relationship (SAR) study of the benzoylalanine side-chain of 1. 2-hydroxy-4-(3,4-dichlorophenyl)-4-oxobutanoic acid (8) and 2-benzyl-4-(3,4-dichlorophenyl)-4-oxo-butanoic acid (10) emerged as the most interesting derivatives. Enantiospecific synthesis for both enantiomers of 8 and diastereomeric salt resolution for those of 10 were successfully applied.

Anticonvulsant activity of PNU-151774E in the amygdala kindled model of complex partial seizures

Summary: Purpose: PNU‐151774E [(S)‐(+)‐2‐(4‐(3‐fluoro‐benzyloxy) benzylamino) propanamide, methanesulfonate] is a novel antiepileptic drug (AED) with a broad spectrum of activity in a variety of chemically and mechanically induced seizures. The objective of this study was to evaluate the activity of PNU‐151774E in the amygdala fully kindled rat model of complex partial seizures, and to compare its effects with those of carbamazepine (CBZ), phenytoin (PHT), lamotrigine (LTG), and gabapentin (GBP), drugs used to treat this disease state.