Aakanksha Khandelwal

U.S. Food and Drug Administration Approval Summary: Brentuximab Vedotin for the Treatment of Relapsed Hodgkin Lymphoma or Relapsed Systemic Anaplastic Large-Cell Lymphoma

The U.S. Food and Drug Administration (FDA) describes the accelerated approval of brentuximab vedotin for patients with relapsed Hodgkin lymphoma and relapsed systemic anaplastic large-cell lymphoma (sALCL). FDA analyzed the results of two single-arm trials, enrolling 102 patients with Hodgkin lymphoma and 58 patients with sALCL. Both trials had primary endpoints of objective response rate (ORR) and key secondary endpoints of response duration and complete response (CR) rate. For patients with Hodgkin lymphoma, ORR was 73% (95% CI, 65–83%); median response duration was 6.7 months, and CR was 32% (95% CI, 23–42%). For patients with sALCL, ORR was 86% (95% CI, 77–95%), median response duration was 12.6 months, and CR was 57% (95% CI, 44–70%). The most common adverse reactions were neutropenia, peripheral sensory neuropathy, fatigue, nausea, anemia, upper respiratory infection, diarrhea, pyrexia, rash, thrombocytopenia, cough, and vomiting. FDA granted accelerated approval of brentuximab vedotin for the treatment of patients with Hodgkin lymphoma after failure of autologous stem cell transplantation (ASCT) or after failure of at least two prior multiagent chemotherapy regimens in patients who are not ASCT candidates, and for the treatment of patients with sALCL after failure of at least one prior multiagent chemotherapy regimen. Clin Cancer Res; 18(21); 5845–9. ©2012 AACR.

Improved Synthesis of Histone Deacetylase Inhibitors (HDIs) (MS-275 and CI-994) and Inhibitory Effects of HDIs Alone or in Combination with RAMBAs or Retinoids on Growth of Human LNCaP Prostate Cancer Cells and Tumor Xenografts

We have developed new, simple, and efficient procedures for the synthesis of two promising histone deacetylase inhibitors (HDIs), CI-994, (N-(2-aminophenyl)-4-acetylaminobenzamide), and MS-275 (N-(2-aminophenyl)4-[N-(pyridine-3-yl-methoxycarbonyl)aminomethyl]benzamide) from commercially available acetamidobenzoic acid and 3-(hydroxymethyl)pyridine, respectively. The procedures provide CI-994 and MS-275 in 80% and 72% overall yields, respectively. We found that the combination of four HDIs (CI-994, MS-275, SAHA, and TSA) with retinoids all-trans-retinoic acid (ATRA) or 13-cis-retinoic acid (13-CRA) or our atypical retinoic acid metabolism blocking agents (RAMBAs) 1 (VN/14-1) or 2 (VN/66-1) produced synergistic anti-neoplastic activity on human LNCaP prostate cancer cells. The combination of 2 and SAHA induced G1 and G2/M cell cycle arrest and a decrease in the S phase in LNCaP cells. 2+SAHA treatment effectively down-regulated cyclin D1 and cdk4, and up-regulated pro-differentiation markers cytokeratins 8/18 and pro-apoptotic Bad and Bax. Following subcutaneous administration, 2, SAHA or 2+SAHA were well tolerated and caused significant suppression/regression of tumor growth compared with control. These results demonstrate that compound 2 and its combination with SAHA are potentially useful agents that warrant further preclinical development for treatment of prostate cancer.

Novel retinoic acid metabolism blocking agents have potent inhibitory activities on human breast cancer cells and tumour growth

Antitumour effects of retinoids are attributed to their influence on cell proliferation, differentiation, apoptosis and angiogenesis. In our effort to develop useful agents for breast cancer therapy, we evaluated the effects of four representative retinoic acid metabolism blocking agents (RAMBAs, VN/14-1, VN/50-1, VN/66-1 and VN/69-1) on growth inhibition of oestrogen receptor positive (ER +ve, MCF-7 and T-47D) and oestrogen receptor negative (ER −ve, MDA-MB-231) human breast cancer cells. Additionally, we investigated the biological effects/molecular mechanism(s) underlying their growth inhibitory properties as well as their antitumour efficacies against MCF-7 and MCF-7Ca tumour xenografts in nude mice. We also assessed the effect of combining VN/14-1 and all-trans-retinoic acid (ATRA) on MCF-7 tumuor xenografts. The ER +ve cell lines were more sensitive (IC50 values between 3.0 and 609 nM) to the RAMBAs than the ER −ve MDA-MB-231 cell line (IC50=5.6–24.0 μM). Retinoic acid metabolism blocking agents induced cell differentiation as determined by increased expression of cytokeratin 8/18 and oestrogen receptor-α (ER-α). Similar to ATRA, they also induced apoptosis via activation of caspase 9. Cell cycle analysis indicated that RAMBAs arrested cells in the G1 and G2/M phases and caused significant downregulation (>80%) of cyclin D1 protein. In vivo, the growth of MCF-7 mammary tumours was dose-dependently and significantly inhibited (92.6%, P<0.0005) by VN/14-1. The combination of VN/14-1 and ATRA also inhibited MCF-7 breast tumour growth in vivo (up to 120%) as compared with single agents (P<0.025). VN/14-1 was also very effective in preventing the formation of MCF-7Ca tumours and it significantly inhibited the growth of established MCF-7Ca tumours, being as effective as the clinically used aromatase inhibitors, anastrozole and letrozole. Decrease in cyclin D1 and upregulation of cytokeratins, Bad and Bax with VN/14-1 may be responsible for the efficacy of this compound in inhibiting breast cancer cell growth in vitro and in vivo. Our results suggest that our RAMBAs, especially VN/14-1 may be useful novel therapy for breast cancer.

Design, Synthesis, and Evaluation of Novel Mutual Prodrugs (Hybrid Drugs) of All-trans-Retinoic Acid and Histone Deacetylase Inhibitors with Enhanced Anticancer Activities in Breast and Prostate Cancer Cells in Vitro

Novel mutual prodrugs (MPs) of ATRA (all- trans-retinoic acid) and HDIs (histone deacetylase inhibitors) ( 10, 13, 17- 19) connected via glycine acyloxyalkyl carbamate linker (AC linker) or through a benzyl ester linker (1,6-elimination linker) were rationally designed and synthesized. Most of our novel MPs were potent inhibitors of growth of several hormone-insensitive/drug resistant breast cancer cell lines and the hormone-insensitive PC-3 prostate cancer cell line. The novel MPs exhibited differential antiproliferative potencies in both MDA-MB-231 and PC-3 cell lines. Whereas 19 (VNLG/124) [4-(butanoyloxymethyl)phenyl(2 E,4 E,6 E,8 E)-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-enyl)nona-2,4,6,8-tetraenoate] with a GI 50 of 10 nM was the most potent MP versus the MDA-MB-231 cells, 13 (VNLG/66) [{ N-[ N-{2-[4-{[3-pyridylmethoxy)carbonyamino]methyl}phenyl) carbonylamino]phenyl} carbamoylcarbamoyloxy}methyl(2 E,4 E,6 E,8 E)-3,7-dimethyl-9-(2,6,6-trimethyl cyclohex-1-enyl)nona-2,4,6,8-tetraenoate] with a GI 50 = 40 nM was the most potent versus the PC-3 cells. MP 19 exhibited the most benefit because its GI 50 of 10 nM versus MDA-MB-231 cells was remarkably 1085-fold lower than that of parent ATRA and over 100000-fold lower than butyric acid (BA).

Potent anti-prostate cancer agents derived from a novel androgen receptor down-regulating agent

The search for novel androgen receptor (AR) down-regulating agents by catalyst HipHop pharmacophore modeling led to the discovery of some lead molecules. Unexpectedly, the effect of these leads on human prostate cancer LNCaP cell viability did not correlate with the ability of the compounds to cause down-regulation of AR protein expression. Through rational synthetic optimization of the lead compound (BTB01434), we have discovered a series of novel substituted diaryl molecules as potent anti-prostate cancer agents. Some compounds (1-6) were shown to be extremely potent inhibitors of LNCaP cell viability with GI(50) values in the nanomolar range (1.45-83 nM). The most potent compound (4-methylphenyl)[(4-methylphenyl)sulfonyl]amine (5) with a GI(50) value of 1.45 nM is 27,000 times more potent than our lead compound BTB01434 (GI(50)=39.8 microM). In addition, some of the compounds exhibited modest anti-androgenic activities and one was also a potent inhibitor (GI(50)=850 nM) of PC-3 (AR-null) cell growth. A clear structure-activity relationship (SAR) has been established for activity against LNCaP cells, where potent molecules possess two substituted/unsubstituted aromatic rings connected through a sulfonamide linker. These novel compounds are strong candidates for development for the treatment of hormone-sensitive and importantly hormone-refractory prostate cancers in humans.

MS-275 synergistically enhances the growth inhibitory effects of RAMBA VN/66-1 in hormone-insensitive PC-3 prostate cancer cells and tumours

Combining drugs, which target different signalling pathways, often decreases adverse side effects while increasing the efficacy of treatment. The objective of our study was to determine if the combination of our novel atypical retinoic acid metabolism-blocking agent (RAMBA) VN/66-1 and a promising histone deacetylase inhibitor N-(2-aminophenyl)4-[N-(pyridine-3-yl-methoxy-carbonyl)aminomethyl]benzamide (MS-275) would show enhanced antineoplastic activity on human PC-3 prostate cancer cells/tumours and also to decipher the molecular mechanisms of action. The combination of VN/66-1+MS-275 was found to be synergistic in inhibiting PC-3 cell growth, caused cell cytostaticity/cytotoxicity and induced marked G2/M phase arrest and apoptosis. In mice with well-established PC-3 tumours, VN/66-1 (5 and 10 mg kg−1 day−1) caused significant suppression of tumour growth compared with mice receiving vehicle alone. Furthermore, treatment with VN/66-1 (10 mg kg−1 day−1)+MS-275 (2.5 mg kg−1 day−1) for 18 days resulted in an 85% reduction in final mean tumour volume compared with control and was more effective than either agent alone. Mechanistic studies indicated that treatment of PC-3 cells/tumours with VN/66-1+MS-275 caused DNA damage (upregulation of γH2AX), hyperacetylation of histones H3 and H4, upregulation of retinoic acid receptor-β, p21WAF1/CIP1, E-cadherin, and Bad and downregulation of Bcl-2. These data suggest that the mechanism of action of the combination of agents is DNA damage-induced p21 activation, resulting in inhibition of the Cdc2/cyclin B complex and accumulation of cells in G2/M phase. In addition, the combination caused modulation and induction of apoptosis. These results suggest that VN/66-1 or its combination with MS-275 may be a novel therapy for the treatment of prostate carcinoma.

VN/14-1 induces ER stress and autophagy in HP-LTLC human breast cancer cells and has excellent oral pharmacokinetic profile in female Sprague Dawley rats

Resistance to aromatase inhibitors is a major concern in the treatment of breast cancer. Long-term letrozole cultured (LTLC) cells represent a model of resistance to aromatase inhibitors. The LTLC cells were earlier generated by culturing MCF-7Ca, the MCF-7 human breast cancer cell line stably transfected with human placental aromatase gene for a prolonged period in the presence of letrozole. In the present study the effect of RAMBA, VN/14-1 on the sensitivity of LTLC cells upon multiple passaging and the mechanisms of action of VN/14-1 in such high passage LTLC (HP-LTLC) cells was investigated. We report that multiple passaging of LTLC cells (HP-LTLC cell clones) led to profound decrease in their sensitivity to VN/14-1. Additionally, microarray studies and protein analysis revealed that VN/14-1 induced marked endoplasmic reticulum (ER) stress and autophagy in HP-LTLC cells. We further report that VN/14-1 in combination with thapsigargin exhibited synergistic anti-cancer effect in HP-LTLC cells. Preliminary pharmacokinetics in rats revealed that VN/14-1 reached a peak plasma concentration (Cmax) within 0.17h after oral dosing. Its absolute oral bioavailability was >100%. Overall these results indicate potential of VN/14-1 for further clinical development as a potential oral agent for the treatment of breast cancer.