Design, synthesis, and evaluation of dual EGFR/AURKB inhibitors as anticancer agents for non-small cell lung cancer

The epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are first-line agents for mutant EGFR-positive (mEGFR+) NSCLC. However, secondary resistant mutations develop following therapy that prevent EGFR-TKI binding. The EGFR-TKIs are rendered ineffective in NSCLC expressing EGFR resistant mutations (rmEGFR+). Mutations in Kirsten rat sarcoma virus protein (mKRAS) support persistent signaling downstream of EGFR regardless of EGFR-TKI earlier in the signaling cascade. The EGFR-TKIs are ineffective in mKRAS+ NSCLC. Thus, newer anticancer agents are needed for rmEGFR+ and mKRAS+ NSCLC. Aurora kinase B (AURKB) is a mitosis related kinase that is overexpressed in NSCLC and supports cancer cell proliferation and survival. Literature reports have suggested that AURKB inhibitors if given concurrently with an EGFR-TKI could overcome EGFR-TKI resistance in mKRAS+ NSCLC and rmEGFR + NSCLC, and showed improved anticancer effects compared to current single-targeted EGFR-TKIs. Molecular modeling was used to identify similarities between the kinase pockets of EGFR and AURKB. An overlap was observed for the inactive conformation of EGFR and the active conformation of AURKB. Compounds 3-7 were synthesized as dual EGFR/AURKB inhibitors for mKRAS+ and rmEGFR+ NSCLC. Compounds 5, 6 and 7 were identified as dual EGFR/AURKB inhibitors. Compound 5 demonstrated modest micromolar inhibition of rmEGFR+ NSCLC. All investigated compounds showed moderate inhibition of mKRAS+ NSCLC cells. Compound 7 demonstrated single-digit micromolar inhibition of mKRAS+ NSCLC.

Comparing Efficacy of Erlotinib and Bevacizumab Combination with Erlotinib Monotherapy in Patients with Advanced Non-Small Cell Lung Cancer (NSCLC): A Systematic Review and Meta-Analysis

The objective of this systematic review and meta-analysis was to assess and contrast the efficacy and safety of combining erlotinib and bevacizumab with erlotinib alone in the treatment of patients with advanced non-small cell lung cancer (NSCLC). The authors searched databases such as PubMed, Medline, Scopus, and Cochrane Central Register of Controlled Trials for randomized control trials (RCTs) comparing erlotinib plus bevacizumab with erlotinib in NSCLC patients. The overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and adverse events (AEs) were the outcomes of interest. The pooled hazard ratio (HR) and relative risk (RR) were estimated utilizing both fixed- and random-effect models. Methodological quality of the included studies was assessed using the Cochrane Risk of Bias tool. Nine studies comprising 1698 patients with NSCLC were included in this meta-analysis, of whom 850 were treated with erlotinib plus bevacizumab, and 848 with erlotinib. The erlotinib plus bevacizumab combination significantly prolonged PFS (HR, 0.62, 95% CI: 0.56, 0.70, p < 0.00001) but did not show any significant improvement in OS (HR, 0.95; 95% CI: 0.83, 1.07, p = 0.39) and ORR (HR, 1.10; 95% CI: 0.98, 1.24, p = 0.09). Increased risks of hypertension (RR, 5.15; 95% CI: 3.59, 7.39; p < 0.00001), proteinuria (RR, 10.54; 95% CI: 3.80, 29.20; p < 0.00001) and grade 3 and higher AEs (RR, 2.09; 95% CI: 1.47, 2.97; p < 0.00001) were observed with the erlotinib-plus-bevacizumab combination compared to erlotinib monotherapy. On subgroup analyses, the erlotinib plus bevacizumab combination improved PFS only. Combining erlotinib and bevacizumab has been shown to improve PFS in advanced NSCLC patients but did not show any significant OS and ORR benefits. Furthermore, risks of hypertension, proteinuria, and grade 3 or higher AEs were greater with the erlotinib-and-bevacizumab combination.

Abstract 5337: Design, synthesis and evaluation of dual-targeted mEGFR and AURK inhibitors as anticancer agents

Mutant epidermal growth factor receptor (mEGFR) inhibitors constitute the recommended therapy for mEGFR-positive cancers. However, resistance has developed to mEGFR inhibitors due to newer mutations within the enzyme pocket and redundant signaling pathways that bypass mEGFR inhibition. Recent studies have shown that resistance to mEGFR inhibitors could be overcome if given in combination with aurora kinase (AURK) inhibitors. Dual EGFR/AURK kinase inhibitors provide a novel approach to overcome resistance to EGFR inhibitors. In a previous study, Kurup et al. identified 1 as a nanomolar mEGFR inhibitor. Using a structure-based design approach, novel analogs of 1 that incorporated varied sidechains for dual mEGFR and AURK inhibition were designed. The synthesis of the target compounds involved microwave-assisted, copper and palladium catalyzed coupling reactions. This study led to the identification of dual-targeted mEGFR/AURKA and mEGFR/AURKB inhibitors, and compounds with sub-micromolar cellular potencies. The design, synthesis, kinase inhibitory activities and anticancer effects of these novel analogs will be presented. Structure-activity relationships for mEGFR, AURKA and AURKB inhibition will be defined.

Citation Format: Dayna Gesinski, Sonali Kurup. Design, synthesis and evaluation of dual-targeted mEGFR and AURK inhibitors as anticancer agents. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5337.

Abstract 5339: 4-Amino-N-phenylbenzamides as dual-targeted mEGFR and AURK inhibitors and anticancer agents

Small molecule, mutant epidermal growth factor receptor kinase (mEGFR) inhibitors are rendered ineffective in NSCLC due to mutations within the enzyme binding sites and redundant signaling pathways. The mEGFR inhibitors were found to retain their anticancer effects in NSCLC cells if given concurrently with AURK inhibitors. Dual-targeted small molecules designed to inhibit both mEGFR and AURK could demonstrate improved anticancer effects compared to monotargeted mEGFR inhibitors. We conducted molecular modeling studies to determine if there were similarities between the kinase pockets of mEGFR and AURK that could be exploited to develop dual-targeted mEGFR and AURK inhibitors. An overlap was observed for the active and allosteric sites of the kinase pocket for mEGFR and AURK. A series of compounds were synthesized and evaluated against mEGFR, AURKA, and AURKB. We found the kinase inhibitory profile to vary significantly depending on the substitution pattern ranging from selective mEGFR inhibitors to dual mEGFR and AURK inhibitors. The 4-substituted amino-N-phenylbenzamides were identified as dual mEGFR/AURK inhibitors. Dual mEGFR/AURK inhibitors demonstrated varied modes of binding within mEGFR and AURK. The most potent dual mEGFR and AURK inhibitors displayed nanomolar inhibition of mEGFR and AURK, and single-digit micromolar inhibition of non-small cell lung cancer cells. Target compounds were further evaluated in a 96-kinase screening assay and demonstrated selectivity for target kinases. The synthesis, structure-activity relationship (SAR) analysis and anticancer effects will be presented and discussed.

Citation Format: Brianne Rogers, Nicholas Rohde, Justin Mikitaroff, Joshua Matson, Samantha Satawa, Felix Amissah, Sonali Kurup. 4-Amino-N-phenylbenzamides as dual-targeted mEGFR and AURK inhibitors and anticancer agents. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5339.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs): a brief overview of clinically approved drugs and combination regimens

The non-nucleoside reverse transcriptase inhibitors (NNRTIs) are allosteric inhibitors of HIV-1 reverse transcriptase and are classified into generations depending on their discovery and resistance profiles. The NNRTIs are used in combination regimens with antiretroviral agents that target two or more enzymes in the viral life cycle. The combination regimens usually include a backbone of two nucleoside or nucleotide reverse transcriptase inhibitors and a third core agent among the NNRTIs or protease inhibitors. The combination regimens are maintained over long durations and consequently lead to long-term problems, including toxicity, drug-drug interactions, and increasing costs. This brief overview summarizes the pharmacokinetic profiles for NNRTIs and NNRTI-based combination regimens.

A meta-analysis comparing therapeutic outcomes for anti-EGFR monotherapy to targeted therapy combinations for non-small cell lung cancer

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Background: Small molecule inhibitors of epidermal growth factor receptor kinase (EGFR) are approved for EGFR-positive non-small cell lung cancer (NSCLC). Targeted therapies include agents that block tumor-specific molecular targets and thereby interfere with tumor growth and metastasis. This study focuses on a meta-analysis of therapeutic outcomes from phase II and III clinical trials for anti-EGFR monotherapy compared to anti-EGFR therapy in combination with targeted agents. Methods: A literature search was conducted using EMBASE, Pubmed, Scifinder Scholar, clinicaltrials.gov and the Cochrane library for the following terms: “epidermal growth factor receptor kinase”, “combination therapy”, “non-small cell lung cancer”. Eligible studies included patients of advanced stage IV NSCLC and any mutation status that met the predefined inclusion criteria. Data was extracted on trial demographics and therapeutic outcomes including progression-free survival (PFS), survival post progression (SPP), overall survival (OS) and adverse events (AE). Sub-group analysis based on patient mutation status of wild-type (wt) EGFR, mutant EGFR, wt KRAS and mutant KRAS and a correlation analysis between OS, PFS and SPP was conducted. Results: A total of 34 studies were identified that fit the inclusion criteria from 2009-2019. The pooled OS hazard ratio (HR) was 0.94 (95% Confidence Interval (CI): 0.87-1.01); the pooled PFS HR was 0.8 (95% CI: 0.74-0.87). Median OS correlated more closely with median SPP (r2 = 0.97 for monotherapy; r2 = 0.88 for combination therapy) than to median PFS (r2 = 0.90 for monotherapy; r2 = 0.82 for combination therapy), although the linear association between log-HR OS and log-HR PFS had a positive slope (β = 0.31± 0.19). A greater incidence of rash and diarrhea was observed in the combination arm compared to monotherapy. A significant improvement was observed for PFS in wt EGFR patients for combination therapy, pooled PFS HR 0.8 (95% CI: 0.67-0.95). Conclusions: A statistically significant improvement in PFS was observed for anti-EGFR combination regimens compared to anti-EGFR monotherapy. The improvement in OS was not statistically significant for anti-EGFR combination regimens compared to monotherapy.

The Journey of HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) from Lab to Clinic

Human immunodeficiency virus (HIV) infection is now pandemic. Targeting HIV-1 reverse transcriptase (HIV-1 RT) has been considered as one of the most successful targets for the development of anti-HIV treatment. Among the HIV-1 RT inhibitors, non-nucleoside reverse transcriptase inhibitors (NNRTIs) have gained a definitive place due to their unique antiviral potency, high specificity, and low toxicity in antiretroviral combination therapies used to treat HIV. Until now, >50 structurally diverse classes of compounds have been reported as NNRTIs. Among them, six NNRTIs were approved for HIV-1 treatment, namely, nevirapine (NVP), delavirdine (DLV), efavirenz (EFV), etravirine (ETR), rilpivirine (RPV), and doravirine (DOR). In this perspective, we focus on the six NNRTIs and lessons learned from their journey through development to clinical studies. It demonstrates the obligatory need of understanding the physicochemical and biological principles (lead optimization), resistance mutations, synthesis, and clinical requirements for drugs.

Abstract 589: A systematic review of randomized clinical trials for therapeutic outcomes of anti-EGFR agents used in combination with other targeted therapies

Introduction: The epidermal growth factor receptor (EGFR) plays a prominent role in cancer cell proliferation and metastasis in non-small-cell lung cancer (NSCLC). Targeted cancer therapies include agents that block tumor-specific molecular targets and thereby interfere with tumor growth, progression and metastasis. This study focuses on a systematic review of outcomes from phase II and III clinical trials for standard anti-EGFR therapy plus a targeted therapy to EGFR monotherapy.

Methods: Studies were identified through a thorough literature search using, EMBASE, Pubmed, Scifinder Scholar, clinicaltrials.gov and the Cochrane library using the following terms: “epidermal growth factor receptor kinase”, “combination therapy”, “non small cell lung cancer”. Eligible studies included patients of any stage and mutation status. Data abstraction included patient demographic characteristics; sample size, patient inclusion and exclusion criteria, overall response rate (ORR), median progression free survival (PFS), median overall survival (OS), and adverse effects (AE).

Results: Literature search resulted in the identification of 1543 studies of which 153 were found to be relevant for this review and 31 fit the inclusion criteria. Of the 31 studies, 28 included erlotinib and 3 studies included gefitinib as the control. Twenty-five of the studies focused on kinase inhibitors targeting VEGFR, EGFR, MET, IGF-1R, AKT, mTOR and HER3 as the combination agent. The remaining six studies focused on alternate pathways of targeted inhibition including hormonal agents and histone deacetylase inhibitors. The identified studies included patients (N=7552) of mean age (63 ± 2), female (22-80%), smokers in combination therapy (12-96%) versus monotherapy (8-95%). Median OS (months) for patients on the EGFR-based combination regimen (range 5.7-24.7) vs monotherapy (range 4.5-21.8). Median PFS (months) for patients on the EGFR-based combination regimen (range 1.3-16.0) vs monotherapy (1.5-9.7). A greater incidence of AE was observed for EGFR-based combination therapy compared to EGFR monotherapy.

Conclusions: Several different targeted therapies have been evaluated as part of clinical trials for NSCLC in combination with EGFR-based therapies, and compared to EGFR-based monotherapy. For patients with NSCLC, a higher range for median OS and median PFS was observed for EGFR-based combination regimens compared to EGFR monotherapy.

Citation Format: Sonali Kurup, Pavlina Liskova, Paiboon Jungsuwadee, Prashant Sakharkar, Soniya Tambe. A systematic review of randomized clinical trials for therapeutic outcomes of anti-EGFR agents used in combination with other targeted therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 589.

Design, synthesis and biological activity of N4-phenylsubstituted-7H-pyrrolo[2,3-d]pyrimidin-4-amines as dual inhibitors of aurora kinase A and epidermal growth factor receptor kinase

Simultaneous inhibition of multiple kinases has been suggested to provide synergistic effects on inhibition of tumour growth and resistance. This study describes the design, synthesis and evaluation of 18 compounds incorporating a pyrrolo[2,3-d]pyrimidine scaffold for dual inhibition of epidermal growth factor receptor kinase (EGFR) and aurora kinase A (AURKA). Compounds 1-18 of this study demonstrate nanomolar inhibition of EGFR and micromolar inhibition of AURKA. Compounds 1-18 allow for a structure-activity relationships (SAR) analysis of the 4-anilino moiety for dual EGFR and AURKA inhibition. Compound 6, a 4-methoxyphenylpyrrolo[2,3-d]pyrimidin-4-amine, demonstrates single-digit micromolar inhibition of both AURKA and EGFR and provides evidence of a single molecule with dual activity against EGFR and AURKA. Compound 2, the most potent inhibitor of EGFR and AURKA from this series, has been further evaluated in four different squamous cell head and neck cancer cell lines for downstream effects resulting from AURKA and EGFR inhibition.

Abstract 4180: RS-41, a multi-targeted kinase inhibitor, induces cell cycle arrest and apoptosis in p53 mutant and wild type models of upper gastrointestinal cancers

Introduction: Upper Gastrointestinal Cancers (UGCs) are a leading cause of cancer-related mortality and account for approximately 1.1 million deaths worldwide. UGCs respond poorly to conventional chemotherapy due to constitutive over activity of multiple oncogenic signaling mechanisms, including the epidermal growth factor receptor (EGFR), ERBB2/HER-2, Aurora kinases, and JAK-STAT pathways. In addition, presence of mutant P53 further imparts resistance to conventional chemotherapeutic agents. Therefore, novel small molecule inhibitors that target multiple kinases associated with oncogenic

progression could pave the way for improved chemotherapy and better therapeutic outcomes. In this study, we characterized the anticancer activity of RS-41, an investigational 4-phenylbenzamidopyrrolo[2,3-d]-pyrimidin-4-amine multi-kinase inhibitor, in P53 mutant and wild type models of UGC.

Methods: Target kinase inhibition and selectivity screening assays were performed to determine potency and selectivity of kinase inhibition for RS-41. In addition, MTT-cell viability assay, clonogenic cell survival assay, cell cycle analyses, and western blot analyses were done to evaluated the effect of RS-41 treatment on cell viability, survival, cell cycle progression, and expression of apoptotic markers in P53 mutant (FLO-1) and P53 wild type (AGS) UGC cells, respectively.

Results: The kinase selectivity screening assay characterized RS-41 for its selectivity against a panel of 90 human kinases. The kinase screening analyses showed that RS-41 selectively inhibits AURKA (IC50-0.96±0.03µM), JAK2 (IC50-1.21±0.17µM), and EGFR (IC50-5.92±0.75µM) kinases, respectively. The cell viability data indicate that treatment with RS-41 mediates significant (P≤0.05) inhibition of FLO-1 and AGS UGC cell viability. The clonogenic cell survival data showed that treatment with RS-41 for 24 hrs. suppresses subsequent formation of colonies in both FLO-1 and AGS UGC cells. The cell cycle data

exhibited a marked increase (P≤0.05) in the percentage of FLO-1 and AGS cells in the sub-G1-phase (cell death) after treatment with RS-41 for 24 and 72 hrs., respectively. The western blotting data further confirmed induction of apoptosis in FLO-1 and AGS cells as evidenced by an increase in expression of various markers of apoptosis (P73/P53, cleaved PARP, and/or cleaved caspase 3) following treatment with RS-41 for 24 and 72 hrs.

Conclusions: Our in vitro data indicate that inhibition of various oncogenic kinases with RS-41 is an effective therapeutic strategy for inducing apoptosis in both P53 mutant and wild type UGC cells. Our study suggests that RS-41 is a promising multi-kinase inhibitor with a potential to further enhance chemotherapeutic options for treatment of UGC.

Citation Format: Tanvi Visal, Shraddha Patel, Priya Pancholi, Samhita Bapat, Amruta Samant, Dhvanir Kansara, Sonali Kurup, Vikas Sehdev. RS-41, a multi-targeted kinase inhibitor, induces cell cycle arrest and apoptosis in p53 mutant and wild type models of upper gastrointestinal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4180. doi:10.1158/1538-7445.AM2017-4180

A Team-based Assignment to Integrate Basic Science and Pharmacotherapeutic Principles for Anticancer Agents

Objective. To implement and evaluate an active-learning, team-based assignment centered on anticancer agents for the integration of basic science and pharmacotherapeutic principles. Methods. Student teams were assigned a specific anticancer agent and were expected to answer a series of questions on the written section of the assignment, followed by a presentation to the class. Each assignment was assessed using a grading rubric that was mapped to the 2013 CAPE educational outcomes. Student perceptions of the assignment were assessed using a short survey. Results. Student cohort performance on the assignment was in the B range (83%) with a mean of 33.2 out of 40. Using the grading rubric, the 12 student cohorts performed particularly well under professionalism (Domain 4.4) that focuses on personal and professional development from CAPE 2013 with means >4 on a 1-5 scale. Student impressions of the assignment suggested that students believed the assignment had a positive effect on their learning and should be continued. Conclusion. The assignment provided a focused review of basic science and pharmacotherapeutic principles and enabled integration of concepts relating to the therapeutic application of anticancer agents, and management of anticancer agent mediated adverse effects. The assignment could contribute toward preparing students for the evolving role of the pharmacist in the management of cancer.

Synthesis of 5,7-disubstituted-4-methyl-7H-pyrrolo[2,3-d]pyrimidin-2-amines as microtubule inhibitors

Compounds 1-4 were previously reported as potent antimitotic and antitumor agents with Pgp modulatory effects. Compounds 5-18 have been synthesized in an attempt to optimize the various activities of 1-4. Compounds 5-10 explored the influence of methoxy substitutions on the 7-benzyl moiety in 1, while 11-18 investigated the influence of incorporation of a sulfur linker at C5 compared to 1-3. Compounds 5-10 demonstrated potent single-digit micromolar tumor cell cytotoxicity, Pgp modulation and microtubule inhibition. Compound 7 of this series was the most potent and showed GI(50) values in the nanomolar range against several human tumor cell lines in the standard NCI preclinical in vitro screen. Antitumor activity and Pgp modulatory effects were found to decrease for the 5-phenylthio compounds 11-14 compared to their 5-phenylethyl analogs 2-4 and the standard compound Taxol. Incorporation of methoxy substitutions on the 7-benzyl moiety improved antitumor activity for the 5-phenylthio compounds 16 and 17. Compounds 16 and 17 demonstrated single to two-digit micromolar inhibition of tumor cells.

N⁴-Aryl-6-substitutedphenylmethyl-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamines as receptor tyrosine kinase inhibitors

Six novel N(4)-substitutedphenyl-6-substitutedphenylmethyl-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamines were synthesized as multiple receptor tyrosine kinase (RTK) inhibitors and antitumor agents. An improvement in the inhibitory potency against epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor 1 (VEGFR-1) and vascular endothelial growth factor receptor 2 (VEGFR-2) assays and in the A431 cellular proliferation assay was observed for compounds 8-13 over the previously reported 5-7. Three compounds (8, 9 and 13) demonstrated potent, multiple RTK inhibition and were more potent or equipotent compared to the lead compounds 5 and 7 and the standard compounds. Compounds 10 and 12 showed potent inhibition of VEGFR-2 over EGFR, platelet-derived growth factor receptor-β (PDGFR-β) and VEGFR-1. The results indicate that the RTK inhibitory profile could be modulated with slight variations to the N(4)-aryl-6-substitutedphenylmethyl-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamino scaffold.

Recent advances in classical and non-classical antifolates as antitumor and antiopportunistic infection agents: Part II

Antifolates that inhibit the key enzymes thymidylate synthase (TS) and dihydrofolate reductase (DHFR) have found clinical utility as antitumor and antiopportunistic agents. Methotrexate {MTX, (1)} and 5-fluorouracil (5-FU) were among the first clinically useful DHFR and TS inhibitors, respectively. The development of resistance to 5-FU, its occasional unpredictable activity and toxicity resulted in the search of novel antifolates. Pemetrexed (4) and raltitrexed (5) are newer antifolates that specifically inhibit TS, and are clinically useful as antitumor agents. A major mechanism of tumor resistance to clinically useful antifolates is based on their need for polyglutamylation via the enzyme folylpoly-gamma-glutamate synthetase (FPGS). Recently, classical antifolates that do not need to be polyglutamylated have also been developed and include plevitrexed (6) and GW1843 (7). Nolatrexed (8), trimethoprim {TMP, (11)} and piritrexim {PTX, (12)} are nonclassical antifolates for antitumor and parasitic chemotherapy that passively diffuse into cells and hence do not have to depend on FPGS or the reduced folate carrier (RFC). Structural requirements for inhibition with antifolates have been studied extensively and novel agents that exploit key interactions in the active site of TS, DHFR, FPGS, and RFC have been proposed. This two-part review discusses the design, synthesis and structural requirements for TS and DHFR inhibition and their relevance to antitumor and parasitic chemotherapy, since 1996. Monocyclic and 6-5 fused bicyclic antifolates were discussed in Part I. The 6-6 bicyclic and tricyclic antifolates will be discussed here in Part II.

Recent advances in classical and non-classical antifolates as antitumor and antiopportunistic infection agents: part I

Antifolates that inhibit the key enzymes thymidylate synthase (TS) and dihydrofolate reductase (DHFR) have found clinical utility as antitumor and antiopportunistic agents. Methotrexate {MTX, (1)} and 5-fluorouracil (5-FU) were among the first clinically useful DHFR and TS inhibitors, respectively. The development of resistance to 5-FU, its occasional unpredictable activity and toxicity resulted in the search of novel antifolates. Pemetrexed (4) and raltitrexed (5) specifically inhibit TS, and are clinically useful as antitumor agents. A major mechanism of tumor resistance to clinically useful antifolates is based on their need for polyglutamylation via the enzyme folylpoly-gamma-glutamate synthetase (FPGS). Novel antifolates have been developed that do not need to be polyglutamylated and include plevitrexed (6) and GW1843 (7). Nonclassical antifolates for antitumor and parasitic chemotherapy, such as nolatrexed (8), trimethoprim {TMP, (11)} and piritrexim {PTX, (12)}, can passively diffuse into cells and hence do not have to depend on FPGS or the reduced folate carrier (RFC). Variations in the structures of antifolates have helped delineate the structural influence on the interaction with TS, DHFR, FPGS, and RFC utilization. The differences in the active site of human and pathogen DHFR have also been exploited. The literature contains excellent reviews on the design and synthesis of antifolates prior to 1996. This two-part review discusses the design, synthesis and structural requirements for TS and DHFR inhibition and their relevance to antitumor and parasitic chemotherapy, since 1996. Monocyclic and 6-5 fused bicyclic antifolates will be discussed in Part I, while 6-6 bicyclic and tricyclic antifolates will be discussed in Part II.

Dihydrofolate reductase as a target for chemotherapy in parasites

Opportunistic infections are known to cause morbidity and mortality in immunocompromised individuals. In addition, serious infections due to several parasites are also known to affect the quality and duration of life in normal individuals. The importance of dihydrofolate reductase (DHFR) in parasitic chemotherapy arises from its function in DNA biosynthesis and cell replication. DHFR catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF), an essential cofactor in the biosynthesis of thymidylate monophosphate (dTMP). Inhibition of DHFR leads to a deficiency of dTMP since DHF cannot be recycled, and thus causes inhibition of cell growth. Methotrexate (MTX) and aminopterin (AMT) were among the first known classical inhibitors of DHFR. Trimethoprim (TMP) and pyrimethamine (PYR) are among the first known non classical inhibitors of DHFR. TMP and PYR are selective but weak inhibitors of DHFR from several parasitic organisms and coadministration of sulfonamides is required to provide synergistic effects for clinical utility. Unfortunately, the side effects associated with sulfa drugs in this combination often result in cessation of therapy. Trimetrexate (TMQ) and piritrexim (PTX) are two potent non classical inhibitors, neither of which exhibit selectivity for pathogen DHFR and must be used with host rescue. However, the current combination therapy suffers from high cost, in addition, several mutations have been reported in the active site of parasitic DHFR rendering the infections refractive to known DHFR inhibitors. The selectivity of TMP is a hallmark in the development of DHFR inhibitors and several efforts have been made to combine the potency of PTX and TMQ with the selectivity of TMP. Thus the structural requirements for DHFR inhibition are of critical importance in the design of antifolates for parasitic chemotherapy. Structural requirements for inhibition have been studied extensively and novel agents that exploit the differences in the active site of human and parasitic DHFR have been proposed. This review discusses the synthesis and structural requirements for selective DHFR inhibition and their relevance to parasitic chemotherapy, since 1995.

Heparan sulphate requirement in platelet-derived growth factor B-mediated pericyte recruitment

HS (heparan sulphate) plays a key role in angiogenesis, by interacting with growth factors required in the process. It has been proposed that HS controls the diffusion, and thus the availability, of platelet-derived growth factor B that is needed for pericyte recruitment around newly formed capillaries. The present paper summarizes our studies on the importance of HS structure in this regulatory process.

Ingress of Bhavnagar City (India)

A preliminary survey of the coastal city-Bhavnagar was undertaken to assess salinity ingress probed through groundwater quality. Water samples from the wells and bores located in the study area were collected and analyzed. Bhavnagar City is found significantly affected by the seawater intrusion. The ground water showed very high values of SO4(-2), Cl(-1), PO4(-3) and, Na(+1), K(+1) compared to the permissible limits for drinking purposes. The quality of ground water in some of the areas was found highly saline and can not be used even for irrigation purpose. The results also indicated a gradual encroachment of seawater into the native ground water.

Correlation of fine needle aspiration cytology, smear and culture in tuberculous lymphadenitis: a prospective study

BACKGROUND AND AIM

Bacteriological studies are necessary to confirm the diagnosis of tuberculous lymphadenitis, as cytological appearances mimic other granulomatous lesions. The objective was to assess the diagnostic role of culture of fine needle aspiration done on clinically suspected cases of tuberculous lymphadenitis and to determine the prevalence of drug resistance in M. tuberculosis isolates.

SETTING AND DESIGN

A prospective, double-blind study over a period of one year in a tertiary care hospital.

MATERIAL AND METHODS

Fine needle aspiration cytology and culture were done on 250 patients with clinical suspicion of tuberculous lymphadenitis.

STATISTICAL ANALYSIS

Data was statistically analysed using chi square test. Sensitivity, specificity, positive predictive and negative predictive values and likelihood ratio were also calculated.

RESULT

Of the 161 cytologically or microbiologically proven cases of tuberculous lymphadenitis, cytological changes consistent with tuberculosis were observed in 133 patients, out of which mycobacteria were isolated in 102 aspirates. Mycobacteria were also isolated from 28 aspirates cytologically missed as tuberculous lymphadenitis. Of the 130-mycobacterial isolates, 5 were non-tuberculous mycobacteria. Culture positivity was significantly higher (P<0.001) than smear positivity. Drug susceptibility studies showed resistance to one or more drugs in 61% of isolated strains with maximum resistance to isoniazid (16% primary and 48% secondary) and minimum to ethambutol (4% primary and 12% secondary).

CONCLUSION

Culture for mycobacteria should be carried out on all aspirates from patients suspected with tuberculous lymphadenitis.

Selective cytotoxicity of MIA Pa Ca-2 conditioned medium to acinar cells: a novel approach to reduce acinar cell contaminants in isolated islet preparations from BALB/c mice

Contamination of acinar cells in islet preparations has been shown to affect islet viability, functionality and yield adversely. Therefore, a strategy which would reduce acinar contamination in islet preparations is much sought. We here demonstrate selective cytotoxicity of conditioned medium (CM) of MIA Pa Ca-2 (human pancreatic carcinoma) cells to acinar cells and suitability of this approach as a simple method of obtaining a pure islet population without affecting their viability and yield. When isolated, islet preparations from BALB/c mice were exposed to conditioned media of MIA Pa Ca-2, acinar cells underwent extensive degeneration to yield 80-85% pure islet population, and islets showed comparable viability to controls not exposed to conditioned media. They also maintained their normal morphology, as assessed by digital image analysis. Islets treated with a conditioned medium also preserved in vitro insulin secretion. Flow cytometric analysis of acinar cells treated with conditioned media revealed accelerated DNA damage (45%), compared to controls (22%). Results emphasize the role of factors secreted by MIA Pa Ca-2 cells in inducing selective toxicity to acinar cells.

The Arabidopsis COMATOSE locus regulates germination potential

Mutation of the COMATOSE locus in Arabidopsis results in a marked reduction in germination potential. Whilst the morphology of comatose (cts) embryos is not altered, physiological analysis reveals that mature cts seeds do not respond to gibberellin. Prolonged chilling of imbibed seeds only partially restores germination potential, and seeds do not after ripen. Genetic analysis shows that the cts phenotype is expressed in the embryo and phenotypic differences between wild-type and mutant plants were not observed during other stages of plant growth and development. Therefore cts represents a new class of mutant, with a specific lesion that results in severely impaired germination potential. Genetic interactions were analysed between cts and loci that regulate embryo maturation, and abscisic acid biosynthesis and perception. Results from these studies showed that the cts mutant phenotype required the wild-type action of these loci, and suggested that CTS exerts a repressive function on these loci. A model is presented postulating that CTS promotes increased germination potential, and represses embryo dormancy. These functions of CTS may result in the removal of embryo dormancy as a prerequisite to germination.

Combined effect of nicotinamide and streptozotocin on diabetic status in partially pancreatectomized adult BALB/c mice

Pancreatic regeneration after pancreatectomy has been well documented in the animal models. We have recently reported that STZ diabetic animals operated for partial pancreatectomy showed normoglycemic status after the operation as compared to uncontrolled hyperglycemia and even death in the diabetic sham operated animals. In drug and virus-induced experimental diabetic models there is a high mortality of animals due to uncontrolled destruction of the beta-cells. In order to destroy sufficient beta-cell mass so as to induce diabetes but prevent mortality, we designed present studies to investigate the combined effect of pancreatectomy, nicotinamide, and streptozotocin (STZ) on diabetic status of BALB/c mice. BALB/c mice of either sex were subjected to 50% pancreatectomy. These were then treated with nicotinamide (350 mg/kg body weight) before and after streptozotocin (200 mg/kg body weight) administration. The changes in body weight, blood glucose levels, serum and pancreatic insulin contents of these animals were monitored in experimental and control group for 12 weeks, and follow up studies were made of these animals for further 12 weeks. It was found that there was a drastic loss of body weight, decreased serum and pancreatic insulin levels coupled with sustained and low levels of hyperglycemia in the experimental group as opposed to the control group. The results indicate that partial pancreatectomy followed by nicotinamide and streptozotocin treatment leads to a long-lasting hyperglycemic state, depicting the clinical symptom of NIDDM without mortality. The study probably reveals a new model for experimental diabetes.

Identification and analysis of proteins that interact with the Avena fatua homologue of the maize transcription factor VIVIPAROUS 1

The Avena fatua (wild oat) homologue of VIVIPAROUS 1 (AfVP1) has been implicated in controlling the maintenance of embryo dormancy in mature imbibed seeds, but the detailed mechanisms by which this transcription factor family activates embryo maturation pathways and simultaneously represses germination are not known. A two-hybrid screen in yeast identified three proteins that interacted specifically with AfVP1 (AfVP1 interacting proteins; AfVIPs). AfVIPs 2 and 3 interacted with the C-terminus of AfVP1, which contains the B2 + B3 domains, previously shown to bind DNA, whereas AfVIP1 interacted with the isolated B3 domain. Using purified proteins in in vitro experiments, all three AfVIPs were shown also to interact with the Arabidopsis homologue ABSCISIC ACID INSENSITIVE 3 (ABI3). The three AfVIPs were expressed in both dormant and non-dormant embryos, but the abundance of AfVIP1 and 3 transcripts was greater in germinated than dormant seeds, whereas transcripts of AfVIP2 (and AfVP1) were more highly expressed in dormant embryos. The AfVIP3 protein has homology to a human cell-crisis gene with a predicted role in the cell cycle; AfVIP2 contains a ring-type zinc finger motif. These homologies, together with analysis of expression studies, suggest that these proteins may play specific roles in AfVP1-mediated regulation of the dormancy to germination transition in A. fatua seeds.

Bio-artificial liver from cultured human foetal hepatocytes: feasibility and prospects

BACKGROUND

Conventional therapy for acute liver failure has not been able to improve survival beyond 40%. Apart from liver transplantation, the most promising development in this field is the utilization of cultured hepatocytes to make 'bio-artificial liver support systems' as a 'bridge to transplantation' or ideally as a 'bridge to total recovery'. This study examines the feasibility of culturing foetal hepatocytes without the use of growth factors and formulating a bio-artificial liver support device in our set-up.

METHODS

Foetal hepatocytes were harvested from the liver obtained from mid trimester abortions at Armed Forces Medical College and Command Hospital (SC), Pune. The liver was perfused with Phosphate Buffered Saline (PBS) and collagenase type IV and was cut with a pair of sterile scissors into tiny pieces. Cells so separated, were washed with PBS plus foetal calf serum and stirred to disperse the cell aggregates. Filtered cell suspensions were inoculated in polystyrene flasks containing hepatocyte culture medium (MEM E: 75%, M199: 25%, BSA: 0.1%, Bovine Insulin 5 micrograms/ml, FCS: 10%, Penicillin: 10 i.u., Streptomycin 50 micrograms/ml, Hydrocortisone 5 micrograms/ml and incubated at 37 degrees C. The functional capabilities of the cultured hepatocytes were analyzed by studying production of albumin and a foetoprotein. Structural integrity of hepatocytes was assessed by light and electron microscopy.

RESULTS

The hepatocyte yield varied from 2 to 60 x 10(6) cells/L with an average of 38 x 10(6) cells/L in the eight consecutive experiments. Initial hepatocyte viability varied from 25% to 90% with an average of 61%. The yield and the viability of hepatocytes were adversely affected by the condition of foetus at birth and use of intra-amniotic injections for inducing abortions. Hepatocyte monolayers and colonies formed in 75% experiments. The cultures could be maintained in incubation without the use of epidermal or hepatocyte growth factors for 2-25 days with a mean survival of 8.9 days. The cells in culture were found to be structurally normal and functionally active and could be cryo-preserved. These hepatocytes were inoculated into a hollow fiber module to formulate bio-artificial liver support device. The cultures ultimately developed either cellular disintegration or bacterial infections despite use of antibiotics in the culture medium.

CONCLUSIONS

We conclude that it is feasible to maintain foetal hepatocyte cultures without the use of expensive growth factors for over 8 days. Bio-artificial liver formulated with cultured foetal hepatocytes is now a step closer to clinical trials.

Interactions of the developmental regulator ABI3 with proteins identified from developing Arabidopsis seeds

The ABI3 locus is a major regulator of embryo development in Arabidopsis and is essential for the simultaneous activation of the maturation pathway, as well as repression of germination and seedling development. We used a two-hybrid screen in yeast in order to identify proteins that interact with ABI3. Four ABI3-interacting proteins (AIPs) were identified which showed specific in vivo and in vitro interactions with the C-terminal region of ABI3 that contains the B2 and B3 domains, previously shown to have DNA binding activity. The expression characteristics of the genes encoding the AIPs have also been analysed in wild-type and abi3, lec1 and fus3 embryo mutants. This analysis demonstrated differential expression of these genes during normal embryo development and in the mutant lines. All the AIPs show homology to existing transcription factors and therefore they may function with ABI3 within the network of transcriptional regulators that control embryo development in Arabidopsis.

Molecular analysis of two functional homologues of the S3 allele of the Papaver rhoeas self-incompatibility gene isolated from different populations

The S3 allele of the S gene has been cloned from Papaver rhoeas cv. Shirley. The sequence predicts a hydrophilic protein of 14.0 kDa, showing 55.8% identity with the previously cloned S1 allele, preceded by an 18 amino acid signal sequence. Expression of the S3 coding region in Escherichia coli produced a form of the protein, denoted S3e, which specifically inhibited S3 pollen in an in vitro bioassay. The recombinant protein was ca. 0.8 kDa larger than the native stigmatic form, indicating post-translational modifications in planta, as was previously suggested for the S1 protein. In contrast to other S proteins identified to date, S3 protein does not appear to be glycosylated. Of particular significance is the finding that despite exhibiting a high degree of sequence polymorphism, secondary structure predictions indicate that the S1 and S3 proteins may adopt a virtually identical conformation. Sequence analysis also indicates that the S1 and S3 proteins may adopt a virtually identical conformation. Sequence analysis also indicates that the P. rhoeas S alleles share some limited homology with the SLG and SRK genes from Brassica oleracea. Previously, cross-classification of different populations of P. rhoeas had revealed a number of functionally identical alleles. Probing of Western blots of stigma proteins from plants derived from a wild Spanish population which contained an allele functionally identical to the Shirley S3 allele with antiserum raised to S3e, revealed a protein (S3s) which was indistinguishable in pI and Mr from that in the Shirley population. A cDNA encoding S3s was isolated, nucleotide sequencing revealing a coding region with 99.4% homology with the Shirley-derived clone at the DNA level, and 100% homology at the amino acid level.