Gina Mangold

The Clinical Effect of the Dual-Targeting Strategy Involving PI3K/AKT/mTOR and RAS/MEK/ERK Pathways in Patients with Advanced Cancer

Purpose: This study evaluated the clinical relevance of the dual-targeting strategy involving PI3K/AKT/mTOR and RAF/MEK/ERK pathways. Experimental Design: We investigated safety, efficacy, and correlations between tumor genetic alterations and clinical benefit in 236 patients with advanced cancers treated with phase I study drugs targeting phosphoinositide 3-kinase (PI3K) and/or mitogen-activated protein kinase (MAPK) pathways in our Phase I Clinical Trials Program. Results: Seventy-six (32.2%) patients received a PI3K pathway inhibitor in combination with a MAPK pathway inhibitor (D), whereas 124 (52.5%) and 36 (15.3%), respectively, received an inhibitor of either the PI3K or MAPK pathways (S). The rates of drug-related grade >III adverse events were 18.1% for (S) and 53.9% for (D; P < 0.001); the rates of dose-limiting toxicities were 9.4% for (S) and 18.4% for (D; P = 0.06). The most frequent grade >III adverse events were transaminase elevations, skin rash, and mucositis. In our comprehensive tumor genomic analysis, of 9 patients who harbored coactivation of both pathways (colorectal cancer, n = 7; melanoma, n = 2), all 5 patients treated with (D) had tumor regression ranging from 2% to 64%. Conclusions: These results suggest that dual inhibition of both pathways may potentially exhibit favorable efficacy compared with inhibition of either pathway, at the expense of greater toxicity. Furthermore, this parallel pathway targeting strategy may be especially important in patients with coexisting PI3K pathway genetic alterations and KRAS or BRAF mutations and suggests that molecular profiling and matching patients with combinations of these targeted drugs will need to be investigated in depth. Clin Cancer Res; 18(8); 2316–25. ©2012 AACR.

An investigation of the antitumour activity and biodistribution of polymeric micellar paclitaxel.

Abstract Purpose: To evaluate in vitro cytotoxicity, in vivo antitumour activity and biodistribution of a novel polymeric (poly(DL-lactide)-block-methoxy polyethylene glycol) micellar paclitaxel. Methods: Hs578T breast, SKMES non-small-cell lung, and HT-29 colon human tumour cells were exposed, either for 1 h or continuously, to conventionally formulated paclitaxel (Cremophor paclitaxel) or polymeric micellar paclitaxel. After a period of incubation, cytotoxicity was measured using a radiometric system. In the in vivo antitumour study, B6D2F1 mice, bearing P388 leukaemia tumour intraperitoneally (i.p.), were treated with polymeric micellar paclitaxel or Cremophor paclitaxel by i.p. injection. The number of deaths and body weights were recorded. In the biodistribution study, CD-1 mice were given micellar paclitaxel i.p. at a dose of 100 mg/kg. The mice were sacrificed after a given time and the organs were harvested. Paclitaxel in the organs was extracted by acetonitrile and analysed using HPLC. Results: The polymeric micellar paclitaxel showed similar in vitro cytotoxicity to Cremophor paclitaxel against the tumour cell lines. The polymeric micellar formulation of paclitaxel produced a fivefold increase in the maximum tolerated dose (MTD) as compared with Cremophor paclitaxel when administered i.p. In addition, micellar paclitaxel was more efficacious in vivo when tested in the murine P388 leukaemia model of malignancy than Cremophor paclitaxel when both were administered i.p. at their MTDs. Micellar paclitaxel-treated animals had an increased survival time and, importantly, long-term survivors (20% of those tested) were obtained only in the polymeric paclitaxel formulation group. Biodistribution studies indicated that a significant amount of paclitaxel could be detected in blood, liver, kidney, spleen, lung and heart of mice after i.p. dosing of the polymeric micellar paclitaxel formulation. Conclusion: These preliminary results indicate that polymeric micellar paclitaxel could be a clinically useful chemotherapeutic formulation.

Enhanced antitumour activity of 6-hydroxymethylacylfulvene in combination with topotecan or paclitaxel in the MV522 lung carcinoma xenograft model.

6-Hydroxymethylacylfulvene (HMAF; MGI 114; Irofulven) is a semisynthetic analogue of the toxin illudin S, which is a product of the Omphalotus mushroom. MGI 114 induces cytotoxicity against a broad range of solid tumours in vivo, including the drug-refractory MV522 human lung cancer xenograft. In this study, the potential application of MGI 114 in the treatment of lung cancer was explored by evaluating the activity of MGI 114 in combination with either topotecan (TPT) or paclitaxel. Groups of eight nude mice bearing MV522 xenografts were treated with MGI 114, TPT or paclitaxel as single agents and with MGI 114 in combination with TPT or paclitaxel. MGI 114 was administered at doses of 2.5 and 5.0 mg/kg intraperitoneally (i.p.) daily on days 1-5, while TPT and paclitaxel were administered at doses of 0.5 or 1.0 mg/kg and 20 mg/kg, respectively, i.p. on days 1-5. In the single-agent studies, MGI 114, TPT and paclitaxel all resulted in decreased final tumour weights compared with vehicle-treated controls. As single agents, TPT, at the 0.5 mg/kg dose level, and paclitaxel, at the 20 mg/kg dose level, produced partial shrinkages (PSs). All combinations of MGI 114, and either TPT or paclitaxel, produced decrements in final tumour weights compared with monotherapy with the same doses of MGI 114, TPT and paclitaxel. Although all animals treated with the combination of MGI 114 and paclitaxel experienced PSs or complete shrinkages (CSs) (or died), analysis of the time to tumour doubling revealed that the combination of MGI 114 and TPT at 2.5 and 0.5 mg/kg, respectively, was synergistic. These results suggest that cytotoxic activity is enhanced when MGI 114 is combined with either TPT or paclitaxel, and clinical trials to further evaluate these combination regimens are warranted.

Preclinical Antitumor Activity and Pharmacokinetics of Methyl-2-Benzimidazolecarbamate (FB642)

Methyl-2-benzimidazolecarbamate(carbendazim, FB642) is an anticancer agentthat induces apoptosis of cancer cells. Invitro, FB642 demonstrated potent antitumoractivity against both the murine B16melanoma (IC50 = 8.5 μm) andhuman HT-29 colon carcinoma(IC50 = 9.5 μm) cell lines. FB642was also highly active against both murinetumor models and human tumor xenografts atvarying doses and schedules. In the murineB16 melanoma model, T/C values > 200 wereobserved. In the human tumor xenograft,FB642 produced tumor growth inhibition ofgreater than 58% in five of the sevenxenograft models evaluated. Partial andcomplete tumor shrinkage was noted withFB642 against the MCF-7 breast tumor model.Pharmacokinetic studies in ratsdemonstrated that oral absorption of FB642was variable and may be saturated at the2000 mg/kg dose level since higher dosesfailed to produce a further increase in thearea under the time concentration curve. Toxicity of FB642 in vivo appeared to bedose-dependent. Lower doses in the range of2000–3000 mg/kg were better tolerated,while still preserving antitumor activity. Evaluation of FB642 in phase I clinicaltrials of adult patients with advancedmalignancies is currently ongoing.

A human breast cancer model for the study of telomerase inhibitors based on a new biotinylated-primer extension assay

SummaryTelomerase is an RNA-dependent polymerase that synthesizes telomeric DNA (TTAGGG)n repeats. The overall goal of our work was to establish human cancer models that can be used to design clinical trials with telomerase inhibitors. The objectives of this study were (1) to set up a human breast cancer system that allows evaluation of the effects of telomerase inhibitors in cultured cells using a non-amplified telomerase assay and (2) to test this system using two drugs (cisplatin and TMPyP4) that affect the telomerase expression in breast cancer cells in culture. We first compared the telomerase activity in a variety of human breast cancer cell lines to that of other tumour types using a new biotinylated-primer extension assay. Our method, based on a non-amplified primer extension assay shows the direct incorporation of 32P-labelled nucleotides induced by telomerase on human telomeric primers. The 32P-dGTP labelled telomerase-extended 5′-biotinylated (TTAGGG)3 primer can subsequently be separated using streptavidin-coated magnetic beads. As compared to other non-amplified method, we showed that this procedure improved the characterization and the quantification of the banding pattern resulting from telomerase extension by reducing the radioactive background. Using this method, we observed that telomerase activity varies markedly in a panel of 39 human cancer cell lines. For example, MCF7 breast cancer cells in culture showed intermediate telomerase activity corresponding to 33.8 ± 3.4% of that of the HeLa cells (reference cell line). Similarly, the telomere length varied with each cell line (average: 6.24 ± 6.16). No correlation between the level of telomerase and telomere length was observed, suggesting that a high processivity is not required to maintain telomeres and that, in some cell lines, another mechanism of telomere elongation can maintain telomere length. From this study, we selected MCF7 and MX1 models that showed reproducible telomerase activity and a relatively limited telomere length for the testing of potential telomere–telomerase interacting agents. Using cisplatin and a new porphyrin-derived compound TMPyP4, we showed that our model was able to detect a down-regulation of the telomerase activity in MCF7 cells in culture and in a human MX1 tumour xenografts. Based on these results, a breast cancer model for evaluating telomerase and telomere interactive agents is proposed.

Evidence of enhanced in vivo activity using tirapazamine with paclitaxel and paraplatin regimens against the MV-522 human lung cancer xenograft

Purpose: Tirapazamine (3-amino-1,2,4-benzotriazine 1,4-dioxide; SR 4233) is a bioreductive agent that exhibits relatively selective cytotoxicity towards cells under hypoxic conditions and can enhance the antitumor activity of many standard oncolytics. In the present study we examined the interaction between tirapazamine in vivo with paclitaxel and paraplatin in two- and three-way combination studies using the MV-522 human lung carcinoma xenograft model. Methods: Agents were administered as a single i.p. bolus, with tirapazamine being given 3 h prior to paclitaxel, paraplatin, or their combination. Tumor growth inhibition (TGI), final tumor weights, partial and complete responses, and time to tumor doubling were determined after drug administration. Results: Tirapazamine as a single agent was ineffective against this human lung tumor model. A substantial increase in TGI was seen in animals treated with the triple-agent regimen (tirapazamine-paclitaxel-paraplatin) compared to animals treated with double-agent regimens that did not include tirapazamine. The addition of tirapazamine to paclitaxel-paraplatin therapy resulted in a 50% complete response rate; there were no complete responses seen when only the paclitaxel-paraplatin combination was administered. Time to tumor doubling was also significantly improved with the addition of tirapazamine to the paclitaxel and paraplatin combinations. Tirapazamine did not increase the toxicity of paclitaxel, paraplatin, or their combinations as judged by its minimal impact on body weight and the fact that no toxic deaths were observed with tirapazamine-containing regimens. Conclusions: These results are important since recent studies have suggested that the combination of paclitaxel and paraplatin may be particularly active in patients with advanced stage non-small-cell lung cancer. Since tirapazamine can significantly improve efficacy, but does not appear to enhance the toxicity of paclitaxel and paraplatin, its evaluation in future clinical trials in combination with paclitaxel-paraplatin-based therapy appears warranted.

Abstract B17: Establishment, characterization and evaluation of a panel of patient-derived colorectal tumor models.

Background: Patient-derived tumor models passaged only a few times in vivo retain physical and molecular characteristics of human cancer and may prove essential in identifying disease biomarkers and drug targets in later stage development. Currently we have collected tumor tissue from chemo-naive and pretreated patients and established and characterized a panel of low passage colorectal tumor models. Methods: For each model, tissue was implanted into immune-deficient mice and once established, each model was confirmed by histologic analysis and linked with donor patient treatment and outcome data. Model characterization including mutation profiling and drug sensitivity studies were performed and results compared with clinical patient information; each model was evaluated with the EGFR inhibitor cetuximab and two standard clinical therapies FOLFOX and irinotecan and compared with patient9s drug sensitivity before and after tissue sample collection. Single agent tumor growth inhibition was evaluated and study endpoints included mean control tumor volumes of approximately 1 cm3 or up to sixty days following treatment initiation. Results: Eighteen low passage colorectal models have been established and characterized. KRAS mutations were identified in 44% of models and activating mutations identified in some models include: PI3KCA (6%), TP53 (33%) and BRAF (6%). In vivo response to FOLFOX and irinotecan correlated to ≥65% of donor patient outcome to these treatments. Cetuximab sensitivity did not fully correlate with Ras mutation status as 4/6 wildtype and 4/8 Ras demonstrated cetuximab sensitivity in these studies. Conclusion: We have generated a panel of low passage colorectal tumor models with differential mutation status and drug sensitivity profiles. Expansion of this panel of patient-derived tumors is planned and should further enhance its utility in identifying agents potentially useful for treatment of colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B17.