Solid Tumor Xenograft Models Research Articles

Phase 2 study of mapatumumab, a fully human agonistic monoclonal antibody which targets and activates the TRAIL receptor-1, in patients with advanced non-small cell lung cancer

Preclinical pharmacological properties of mapatumumab (agonistic human monoclonal antibody to TRAIL-R1) suggest that this antibody reduces cell viability, induces cell death in many types of cancer cell lines in vitro, inhibits or reduces tumor growth in xenograft models of solid tumors, and can induce significant tumor regression in some models. The receptor for mapatumumab, TRAIL-R1, is expressed on NSCLC cell lines. This pharmacologic profile suggests that mapatumumab may have therapeutic benefit in the treatment of NSCLC. This Phase 2 multi-center study was designed to evaluate the efficacy, safety, and tolerability of mapatumumab in patients with advanced non-small cell lung cancer (NSCLC) previously treated with at least 1 platinum-based regimen. Each patient was to receive mapatumumab at a dose of 10mg/kg administered intravenously (IV) every 21 days in absence of disease progression. A total of 32 patients with relapsed or refractory Stage IIIB or IV or recurrent NSCLC were enrolled. Patients had received a median of 3 previous therapeutic regimens (range 1-7). Mapatumumab was well tolerated by the patients in this study with no discontinuations due to adverse events. The most common adverse events reported, regardless of relationship, were fatigue, cough, nausea, dyspnea, constipation, and vomiting. Laboratory analyses revealed no appreciable evidence of hepatic or renal toxicity among the study patients. No patients developed anti-mapatumumab antibodies. The plasma mapatumumab concentrations observed in this study were consistent with the predicted exposures, based on Phase 1 pharmacokinetic results. None of the 32 treated patients showed a response according to the RECIST criteria. Nine patients (29%) had stable disease (SD). In a group of heavily pretreated NSCLC patients, no objective single agent activity of mapatumumab was demonstrated, but the drug was safe and well tolerated. Based on this favorable safety profile, and preclinical evidence of potential synergy in combination with agents commonly used to treat NSCLC, future evaluation of mapatumumab in combination with chemotherapy is warranted.

Selenium Enhances the Anti-Angiogenic Effects of Bevacuzimab (Anti-VEGF Antibody) in Human Acute Myeloid Leukemia Xenograft Models.

Selenium, a known antioxidant used in chemoprevention, has recently been shown to improve the efficacy of chemotherapy agents and mediate anti-angiogenic effects in preclinical solid tumor models. Prior data has also shown that sodium selenite can induce apoptosis of human acute myeloid leukemia (AML) cells in vitro. While the use of high non-toxic doses of selenium has been demonstrated to effectively enhance the therapeutic efficacy and selectivity of various anti-cancer drugs in multiple solid tumor xenograft models (Cao et al, Clin Canc Res 10: 2561–2569, 2004), the in vivo effects of selenium compounds in hematological malignancies have not been extensively explored. Our laboratory has previously demonstrated the preclinical efficacy of VEGF inhibitors in human leukemia xenograft models. Here we investigated the in vitro and in vivo effects of seleno-L-methionine (SLM), alone and in combination with chemotherapy and anti-VEGF antibody, in human AML. The mechanism of action, dosage, and time course of SLM effects on AML cells (ML-2 and HL60) in vitro were determined using colorimetric (CCK-8) viability, tritiated thymidine proliferation, and Annexin-V flow cytometric assays. SLM therapy resulted in dose dependent inhibition of AML proliferation with marked induction of apoptosis and a 67–92% reduction in viable cells at 400–500 μM. Ten million AML cells (ML-2 and HL60-luciferase) were then subcutaneously engrafted into immunodeficient (SCID/SCID) mice. ML-2 tumor bearing mice were treated with PBS (vehicle), SLM (200 mcg p.o. daily), cytarabine (Ara-C 2 mg i.p. for 3 days), or combination SLM + Ara-C therapy for over two weeks. SLM showed no effective modulation of therapeutic efficacy and toxicity in AML tumor models, when combined with Ara-C. Neither SLM nor Ara-C alone or in combination resulted in significant reduction of AML growth. ML-2 and HL60-luciferase tumor bearing mice were then treated with PBS, SLM (200 mcg p.o. daily), anti-VEGF antibody bevacuzimab (BV 100mcg i.p. twice weekly), or SLM + BV for three weeks. Disease progression was monitored by tumor volume, end tumor weight, and bioluminescent imaging. Although SLM alone was ineffective in reducing HL60 leukemia growth, SLM + BV combination therapy effectively induced a 75% reduction in mean tumor volume after 21 days of treatment which was statistically greater than BV therapy alone (62% reduction). Synergistic effects of SLM+BV therapy was also confirmed by differences in mean tumor weights and bioluminescent imaging as compared with single agent BV and SLM treated mice. Similar results were seen in the ML-2 AML xenograft model.Conclusions: SLM improved the anti-angiogenic and anti-tumor effects of anti-VEGF therapy with bevacizumab in human AML xenograft models. Additional studies investigating the mechanisms of action of these synergistic effects will be presented.

Subgroup analysis of efficacy and safety analysis of a randomized, double-blinded controlled phase II study of STA-4783 in combination with paclitaxel in patients with metastatic melanoma

8528 Background: STA-4783 (S), an inducer of heat shock protein 70 (hsp70) is a bis-thiobenzoylhydrazide compound. S leads to up-regulation of hsp70 in tumor cell lines. Xenograft models of solid tumors showed synergistic anti-tumor activity in combination with paclitaxel (P). The combination P + S, in phase I and II studies, showed dose-related hsp70 induction (evidence of biological activity) and tolerability. Methods: Eligibility was based on a diagnosis of metastatic cutaneous melanoma, ECOG <=2, and prior treatment with 1 or no chemotherapy regimens. A total of 81 patients (pts) were randomized 2:1 (P 80 mg/m2 + S 213 mg/m2:P 80 mg/m2) 3 weeks out of 4 at 21 US clinical sites. The primary endpoint was progression free survival (PFS); secondary endpoints were response rate (RR), and adverse events (AEs). Results: Based on intent-to-treat analysis, the median PFS was 3.68 months (m) for P + S vs. 1.84 m in the P only arm (p=.035). RR was 15.1% in the P + S arm and 3.6% in the P arm. Subgroup analysis showed chemo- naive pts (n=23) with P + S showed a median PFS of 8.28 m vs. 2.40 in the P arm (n=9). For pts with 1 prior chemotherapy, (n=29), PFS on P + S was 3.12 m vs. 1.77 m on P (n=19). Of 19 pts who crossed over at progression, data are available for 14. PFS ranged from 0.72 to 5.5 m. Three of the 14 evaluable pts treated with P alone had rapid progression (0.95, 1.6, and 1.7 m) then significant inversion of the time to progression with the addition of S to P (2.3, 5.5, and 4.2 m) suggesting study drug effect. Scans were done at identical intervals (8 weeks). The proportion of pts with AEs of grade 3 or higher was 54% (n=52) in the P + S group and 57% in the P group (n=28); pts on P received a median of 2 cycles, while pts in the P + S group received a median of 4. Adverse events leading to discontinuation were low in both groups: 10% for the P + S, and 14% for P. Conclusions: The addition of S to P showed an increase in PFS vs. P alone particularly in chemo-naïve pts. A few pts failing single agent P appeared to benefit from P + S. Despite the additional treatment duration in the P + S group the drugs were well- tolerated, and showed mainly P related adverse events. A phase III study is planned to confirm a role for P + S in metastatic melanoma. [Table: see text]

Initial testing of cisplatin by the pediatric preclinical testing program

Cisplatin is one of the most widely used drugs for the treatment of solid tumors in adults and children. Here, we report the activity of cisplatin against the PPTP panels of childhood cancer xenografts. Cisplatin was evaluated against 23 cell lines, and 40 xenografts representing brain tumors, neuroblastoma, rhabdoid tumors, sarcoma, Wilms tumor, and acute lymphoblastic leukemia (ALL). The IC(50) concentration in vitro was determined for 96 hr exposure. Solid tumors were grown subcutaneously in immune-deficient mice, and tumor dimensions measured weekly. ALL xenografts were inoculated intravenously and the percent human CD45(+) cells in the peripheral blood determined weekly. The antitumor activity of cisplatin (7 mg/kg administered intraperitoneally on Days 0 and 21) was evaluated using time to event (EFS T/C), tumor growth delay (tumor volume T/C), and objective response measures. The median IC(50) concentration in vitro was 0.87 microM (0.24-4.29 microM), and cisplatin exhibited broad range activity. Cisplatin induced significant differences in EFS distributions compared to controls in 20/28 solid tumors and 4/8 ALL models. Objective responses were observed in 7/28 solid tumor models (25%): partial responses in three rhabdomyosarcomas and one Ewing's sarcoma; complete responses in one rhabdoid tumor and the medulloblastoma; and a maintained complete response in one Wilms tumor. No objective responses were observed in the ALL panel. Cisplatin exhibits significant antitumor activity against a broad range of solid tumor xenograft models and limited activity against ALL xenografts. This preclinical pattern of activity is generally consistent with cisplatin's clinical activity.

Synthesis and Src Kinase Inhibitory Activity of a Series of 4-[(2,4-Dichloro-5-methoxyphenyl)amino]-7-furyl-3-quinolinecarbonitriles

Compound 1 (SKI-606, bosutinib), a 7-alkoxy-4-[(2,4-dichloro-5-methoxyphenyl)amino]-3-quinolinecarbonitrile, is a potent inhibitor of Src kinase activity. We previously reported that analogs of 1 with thiophene groups at C-7 retained the Src activity of the parent compound. The corresponding C-7 furan analogs were prepared and it was found that the 3,5-substituted furan analog had increased activity compared to that of the 2,5-substituted furan isomer. Addition of a methoxy group at C-6 decreased the Src inhibitory activity of the C-7 2,5-substituted furan analog but increased the activity of the C-7 3,5-substituted furan isomer. This compound, 10, was a more potent Src inhibitor than 1 in both enzymatic and cell-based assays. The kinase selectivity profile of 10 was similar to that of 1, with 10 also inhibiting the activity of Abl and Lck. When tested in a solid tumor xenograft model, 10 had comparable oral activity to that of 1.

378 POSTER Sequence dependent anti-tumor activity of bortezomib and the KSP inhibitor, SB743921, in a solid tumor xenograft model

378 POSTER Sequence dependent anti-tumor activity of bortezomib and the KSP inhibitor, SB743921, in a solid tumor xenograft model

In vivo antitumor activity by 2?,4?-dihydroxy-6?-methoxy-3?,5?-dimethylchalcone in a solid human carcinoma xenograft model

Previously, we showed that 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), isolated from the buds of Cleistocalyx operculatus, significantly inhibited the growth of human liver cancer SMMC-7721 cells and could induce SMMC-7721 cells apoptosis in vitro. Here, we report the antitumor effects of DMC in vivo, using a solid human tumor xenograft model with a human liver cancer SMMC-7721 cell line. Our results revealed that the average tumor weight in a control group and a 150-mg/kg DMC injection group was 1.42+/-0.11 g and 0.59+/-0.12 g, respectively. Flow cytometric analysis of the tumor cell population demonstrated the existence of an aneuploid peak (representing 33.60+/-0.80% of the total in the 150-mg/kg DMC injection group). To our knowledge, this is the first time that chalcone compounds were applied to a human tumor xenograft model.

Enhanced antitumor activity of irofulven in combination with irinotecan in pediatric solid tumor xenograft models

Irofulven, a novel chemotherapeutic agent with a broad spectrum of activity, is effective against preclinical models of pediatric tumors. The cytotoxic activity of irofulven is augmented when combined with agents that interact with DNA topoisomerase I; however, none of the reported studies have used the protracted dosing schedule found to be active clinically in treatment of childhood cancers. The objective of this study was to evaluate the antitumor activity of irofulven in combination with irinotecan administered on a protracted schedule in a panel of pediatric solid tumor xenografts. Irofulven and irinotecan were evaluated alone or in combination against eight independent xenografts, which included childhood brain tumors (n=5), neuroblastoma (n=1), and rhabdomyosarcoma (n=2). Irofulven was administered i.v. daily for 5 days with courses repeated every 21 days for a total of three cycles. Doses of irofulven ranged from 1.33 to 4.6 mg/kg. Irinotecan was given i.v. daily for 5 days each week for 2 weeks repeated every 21 days for three cycles at doses between 0.28 and 1.25 mg/kg. Irofulven and irinotecan, given as single agents, induced few responses in pediatric solid tumor xenografts at the selected doses. At the same doses, irofulven in combination with irinotecan demonstrated superior antitumor activity, inducing complete responses in seven of the eight xenograft lines. These studies show that the cytotoxic activity of irofulven is greater when combined with protracted administration of irinotecan. Although the systemic exposure of irofulven required to induce objective responses in this panel of pediatric solid tumors was in excess of that achievable in patients receiving maximally tolerated doses using this schedule of drug administration, the enhanced activity of irofulven in combination with irinotecan supports the pursuit of alternative administration strategies and combinations.

Polymerization of the triphosphates of AraC, 2′,2′-difluorodeoxycytidine (dFdC) and OSI-7836 (T-araC) by human DNA polymerase α and DNA primase

OSI-7836 (4′-thio-araC, T-araC) is a nucleoside analogue that shows efficacy against solid tumor xenograft models. We examined how the triphosphates of OSI-7836 (T-araCTP), cytarabine (araCTP), and gemcitabine (dFdCTP) affected the initiation of new DNA strands by the pol α primase complex. Whereas dFdCTP very weakly inhibited primase, both T-araCTP and araCTP potently inhibited this enzyme. Primase polymerized T-araCTP and araCTP more readily than its natural substrate, CTP, and incorporation resulted in strong chain termination. dFdCTP, araCTP, and T-araCTP inhibited pol α competitively with respect to dCTP. When exogenously added primentemplates were used, pol α incorporated all three analogues into DNA, and incorporation caused either weak chain termination (dFdCTP), strong termination (araCTP), or extremely strong termination (T-araC). Furthermore, pol α polymerized T-araCTP only nine-fold less well than dCTP, whereas it polymerized araCTP and dFdCTP 24- and 83-fold less well, respectively. The presence of these three analogues in the template strand resulted in significant pausing by pol α, although the site and severity of pausing varied between the analogues. During the elongation of primase-synthesized primers, a reaction that is thought to mimic the normal sequence of events during the initiation of new DNA strands, pol α polymerized all three compounds. However, incorporation of araCTP and dFdCTP resulted in minimal chain termination, while incorporation of T-araCTP still caused extremely strong termination. The implications of these results with respect to how these compounds affect cells are discussed.

Clinical and dynamic imaging results of the first phase I study of AG–013736, an oral anti-angiogenesis agent, in patients (pts) with advanced solid tumors

2503 Background: AG-013736 is a potent and selective inhibitor of VEGF and PDGF receptor tyrosine kinases with broad preclinical activity in xenograft models of solid tumors. Methods: The primary objective was to determine maximum tolerated dose (MTD) and safety. Efficacy, pharmacokinetics (PK), and tumor vascular response were also evaluated. AG–013736 was administered orally once or twice daily in 28-day cycles in escalating doses to pts with solid tumors. Results: 36 pts in 6 cohorts were treated. At least 2 cycles of data are available on the first 30. Tumor diagnoses: breast (11), thyroid (5), renal cell (5), lung (4), and other (5). The MTD was 5 mg twice daily (BID) fasted (no food or beverage within 2 hours of dose). Toxicity: Dose-limiting toxicities (DLTs) at doses >MTD (16 pts) were hypertension (HTN) (6 pts); seizures associated with HTN (2); elevated liver function tests (2); mesenteric vein thrombosis and pancreatitis (1); and stomatitis (2). One pt with a cavitating lung lesion died of hemoptysis while on drug. At doses ≤MTD (14 pts), DLT was limited to grade 2 stomatitis in 1 pt; non-dose limiting HTN, managed by conventional antihypertensive meds, was observed in 6 pts. Response: Two durable partial responses (10+, 5 mo) by RECIST criteria were observed (in renal cell and adenoid cystic carcinomas); 7 pts had stable disease lasting ≥4 mo. PK: AG-013736 plasma concentrations were variable (39%–96% CV), linear within the dose range, with peaks at 2–4 h, and terminal half-life of 3–5 h. Plasma exposures were higher (∼ 49%) and intra-pt variability was reduced in the fasted vs fed state. Vascular response: Dynamic contrast enhanced MRI was performed at baseline, and after 2, 28, and 56 days of therapy. The % change in mean Ktrans and initial area under the contrast intensity X time curve (IAUC) was computed. 6 of 18 pts with evaluable serial scans had a tumor vascular response, defined as ≥50% decrease from baseline parameter values to day 2; correlation with PK and response will be reported. Conclusions: There is sufficient safety and activity of AG–013736 to warrant Phase II trials at a recommended dose of 5 mg BID fasted. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Pfizer, Inc. Pfizer, Inc. Pfizer, Inc. Pfizer

Clinical and dynamic imaging results of the first phase I study of AG–013736, an oral anti-angiogenesis agent, in patients (pts) with advanced solid tumors

2503 Background: AG-013736 is a potent and selective inhibitor of VEGF and PDGF receptor tyrosine kinases with broad preclinical activity in xenograft models of solid tumors. Methods: The primary objective was to determine maximum tolerated dose (MTD) and safety. Efficacy, pharmacokinetics (PK), and tumor vascular response were also evaluated. AG–013736 was administered orally once or twice daily in 28-day cycles in escalating doses to pts with solid tumors. Results: 36 pts in 6 cohorts were treated. At least 2 cycles of data are available on the first 30. Tumor diagnoses: breast (11), thyroid (5), renal cell (5), lung (4), and other (5). The MTD was 5 mg twice daily (BID) fasted (no food or beverage within 2 hours of dose). Toxicity: Dose-limiting toxicities (DLTs) at doses >MTD (16 pts) were hypertension (HTN) (6 pts); seizures associated with HTN (2); elevated liver function tests (2); mesenteric vein thrombosis and pancreatitis (1); and stomatitis (2). One pt with a cavitating lung lesion died of hemoptysis while on drug. At doses ≤MTD (14 pts), DLT was limited to grade 2 stomatitis in 1 pt; non-dose limiting HTN, managed by conventional antihypertensive meds, was observed in 6 pts. Response: Two durable partial responses (10+, 5 mo) by RECIST criteria were observed (in renal cell and adenoid cystic carcinomas); 7 pts had stable disease lasting ≥4 mo. PK: AG-013736 plasma concentrations were variable (39%–96% CV), linear within the dose range, with peaks at 2–4 h, and terminal half-life of 3–5 h. Plasma exposures were higher (∼ 49%) and intra-pt variability was reduced in the fasted vs fed state. Vascular response: Dynamic contrast enhanced MRI was performed at baseline, and after 2, 28, and 56 days of therapy. The % change in mean Ktrans and initial area under the contrast intensity X time curve (IAUC) was computed. 6 of 18 pts with evaluable serial scans had a tumor vascular response, defined as ≥50% decrease from baseline parameter values to day 2; correlation with PK and response will be reported. Conclusions: There is sufficient safety and activity of AG–013736 to warrant Phase II trials at a recommended dose of 5 mg BID fasted. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Pfizer, Inc. Pfizer, Inc. Pfizer, Inc. Pfizer

A Phase I Study of Gefitinib and irinotecan (IRN) in pediatric patients with refractory solid tumors

8521 Background: Gefitinib (Iressa), an oral Epidermal Growth Factor receptor (EGFR) inhibitor that has been well tolerated in adults, modulates intracellular drug effects through inhibition of efflux pumps (e.g., BCRP). In xenograft models of pediatric solid tumors it has additive/synergistic activity with IRN, which was independent of EGFR status. We are conducting a Phase I study of this combination in children with refractory solid tumors. Methods: Our objectives are to estimate the maximum tolerated dose and dose-limiting toxicities (DLT) of gefitinib administered daily × 21 days in combination with protracted intravenous IRN [day 1- 5, day 8 - 12]. Pharmacokinetic (PK) studies of IRN and metabolites were obtained with and without concurrent gefitinib. PK studies of gefitinib were obtained on days –1 and 8. Courses are repeated every 21 days in the absence of DLT or disease progression. Results: At present, 2 cohorts have been evaluated (age 3 –15 yrs, median 5 yrs). Cohort 1 (n = 5) received continu...

Preclinical activity of an i.v. formulation of rubitecan in IDD-P against human solid tumor xenografts.

An i.v. formulation of rubitecan (9-nitrocamptothecin) was evaluated in five human solid tumor xenograft models. Rubitecan in IDD-P, a particulate suspension of the insoluble analog, produced significant tumor growth delay in athymic nude mice bearing A375 melanoma, and MX-1 breast, SKMES non-small-cell lung, Panc-1 pancreatic and HT29 colon carcinomas. The activity of i.v. rubitecan was similar or somewhat superior to those of i.p. regimens with the reference drugs, irinotecan and topotecan. Tumor sensitivity to rubitecan in IDD-P was MX-1>A375>SKMES >Panc-1>HT29. Some complete regression responses were seen with MX-1, A375 and SKMES tumors treated with 2.5 mg/kg on a schedule of two 5-day dosing cycles separated by 2 drug-free days. In nude mice, the MTD of rubitecan in IDD-P lies between 2 and 2.5 mg/kg on this schedule; antitumor efficacy was achieved with doses between 2.5 and 1.25 mg/kg. Dosing with 6.6 mg/kg rubitecan in IDD-P on intermittent schedules (4- or 7-day intervals) was tolerated, but less efficacious, when tested in the A375 model. The good responses obtained with rubitecan in IDD-P suggest it could be used clinically in circumstances where an i.v. formulation offers advantages to oral or aerosol formulations.

Increased intracellular drug accumulation and complete chemosensitization achieved in multidrug-resistant solid tumors by co-administering valspodar (PSC 833) with sterically stabilized liposomal doxorubicin.

We have previously demonstrated that liposome encapsulation of doxorubicin (DOX) can alleviate adverse interactions with non-encapsulated DOX and the cyclosporine multidrug-resistant (MDR) modulator Valspodar. We have now investigated the behavior of different liposomal DOX formulations in MDA435LCC6/MDR-1 human breast cancer solid tumor xenograft models to identify liposome characteristics associated with enhanced therapeutic activity and the mechanism whereby increased chemosensitization is achieved. Toxicity studies incorporating conventional phosphatidylcholine (PC)/cholesterol (chol) and sterically stabilized (polyethylene glycol 2000 [PEG]-containing) formulations of DOX indicated that whereas PC/Chol DOX was approximately 3-fold more toxic in the presence of Valspodar, PEG containing distearoylglycerophosphocholine (DSPC)/Chol DOX was minimally affected. In mice bearing MDR tumors, co-administration of Valspodar and egg phosphocholine (EPC)/Chol DOX resulted in modest MDR modulation and efficacy, whereas the sterically stabilized formulation induced reductions in tumor growth equivalent to that achieved for drug-sensitive tumors treated with non-encapsulated DOX. Pharmacokinetic studies revealed a 2.5-fold increase in plasma DOX area under the curve (AUC) upon co-administration of Valspodar with EPC/Chol DOX whereas no such alterations were observed with the sterically stabilized liposomes. Compared to non-encapsulated DOX combined with Valspodar, improvements in efficacy and toxicity correlated with the extent to which liposomal DOX formulations were able to circumvent pharmacokinetic interactions. Confocal microscopy demonstrated that Valspodar increased cell-associated DOX which correlated with the level of anti-tumor efficacy.