Phase 1 study of KT-413, a targeted protein degrader, in adult patients with relapsed or refractory B-cell non-Hodgkin lymphoma

TPS3170

Background: Oncogenic mutations in myeloid differentiation primary response 88 (MYD88) occur in approximately 25% of diffuse large B-cell lymphoma (DLBCL) cases, including approximately 30% of activated B-cell DLBCL and up to 70% of primary extranodal DLBCL, and are associated with poor survival following 1st line therapy. MYD88 mutations result in activation of the NF-κB pathway which drive a range of pro-tumor activities including upregulation of proinflammatory cytokines and genes involved in tumor cell proliferation and survival. Activation of this pathway results in upregulation of IRF4 through the transcription factors Ikaros and Aiolos, which in turn further augments NF-kB activation while simultaneously downregulating Type I IFN signaling, thereby preventing oncogene-induced cell death. Constitutive NF-kB pathway activation resulting from MYD88 mutations is dependent on the interleukin-1 receptor associated kinase 4 (IRAK4), a key component of the myddosome complex which normally stimulates NF-kB signaling following TLR or IL-1R engagement and MYD88 activation. KT-413 is a potent and selective heterobifunctional small molecule protein degrader mediating the degradation of both IRAK4 and the IMiD substrates Ikaros and Aiolos via the ubiquitin-proteasome system. The therapeutic hypothesis is that degradation of IRAK4 and IMiD substrates will maximize NF-κB inhibition while simultaneously upregulating the Type I Interferon response, thus restoring the apoptotic response and enabling oncogene-mediated cell death, resulting in robust antitumor response in MYD88-mutant DLBCL. KT-413 induced strong antitumor activity, including complete or partial regressions, in cell line- and patient-derived xenograft models of MYD88MT DLBCL (Mayo 2021). Methods: KT-413 is being evaluated in an open label, dose escalation (Phase 1a) study in patients with relapsed/refractory (R/R) B-cell non-Hodgkin lymphoma (NHL), followed by dose expansion (Phase 1b) in patients with R/R DLBCL with documented tumor MYD88 mutation status. All patients must be ineligible or refused auto-SCT or CAR-T therapy. The Phase 1a (n = 40) utilizes an accelerated titration followed by a 3+3 design in ascending doses of IV administered KT-413 in once every 21-day cycles to identify the maximum tolerated dose (MTD)/recommended Phase 2 dose (RP2D) (primary endpoint). Secondary endpoints include pharmacokinetics (PK) and preliminary pharmacodynamic effects (PD) using blood and tumor tissue. Once MTD/RP2D is determined in 3-6 patients, it will be confirmed by enrolling additional patients with B-cell NHL, for a total of nine. In Phase 1b, up to 40 R/R DLBCL patients will be enrolled into one of two cohorts (n = 20): MYD88MT or MYD88WT to further characterize tolerability, PK, PD and evaluate the clinical activity of KT-413. KT413-DL-101 began enrollment in February 2022. Clinical trial information: NCT05233033.

Pharmacokinetics and safety of niraparib in patients with moderate hepatic impairment

PURPOSE

The purpose of this study is to characterize niraparib pharmacokinetics (PK) and safety in patients with normal hepatic function (NHF) versus moderate hepatic impairment (MHI).

METHODS

Patients with advanced solid tumors were stratified by NHF or MHI (National Cancer Institute-Organ Dysfunction Working Group criteria [bilirubin > 1.5-3 × upper limit of normal and any aspartate aminotransferase elevation]). In the PK phase, all patients received one 300 mg dose of niraparib. In the extension phase, patients with MHI received niraparib 200 mg daily; patients with NHF received 200 or 300 mg based on weight (< 77 kg, ≥ 77 kg)/platelets (< 150,000/µL, ≥ 150,000/µL). PK parameters included maximum concentration (C_max), area under the curve to last measured concentration (AUC_last) and extrapolated to infinity (AUC_inf). Safety was assessed in both phases. Exposure-response (E-R) modeling was used to predict MHI effects on exposure and safety of niraparib doses ≤ 200 mg or 300/200 mg or 200/100 mg weight/platelet regimens.

RESULTS

In the PK phase (NHF, n = 9; MHI, n = 8), mean niraparib C_max was 7% lower in patients with MHI versus NHF. Mean exposure (AUC_last, AUC_inf) was increased by 45% and 56%, respectively, in patients with MHI without impacting tolerability. In the extension phase (NHF, n = 8; MHI, n = 7), the overall safety profile was consistent with previous trials. In patients with MHI, E-R modeling predicted niraparib 200 mg reduced Grade ≥ 3 thrombocytopenia incidence, whereas a 200/100 mg regimen yielded exposures below efficacy-associated levels in 15% of patients.

CONCLUSION

These findings support adjusting the 300 mg niraparib starting dose to 200 mg QD in patients with MHI.

TRIAL REGISTRATION

NCT03359850; registered December 2, 2017.

Pharmacokinetics and safety following a single oral dose of niraparib in patients with moderate hepatic impairment

6054

Background: Niraparib is approved for the maintenance treatment of adult patients (pts) with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinum-based chemotherapy, or with similar cancers but advanced, associated with homologous recombination deficiency (HRD) and have been treated with ³3 prior chemotherapy regimens. Niraparib is extensively metabolized in the liver and eliminated via both hepatobiliary and renal routes. Objectives of this study included characterization of niraparib pharmacokinetics (PK) and safety in pts with normal hepatic function vs. pts with moderate hepatic impairment. Methods: This phase I, open-label, parallel-group, single-dose study enrolled pts with advanced solid tumors into 2 groups: normal hepatic function and moderately impaired hepatic function, defined as bilirubin >1.5 to 3 times the upper limit of normal and any aspartate aminotransferase elevation. Pts received a single 300-mg dose and underwent PK sampling for 7 days. Exposure parameters included maximum concentration (Cmax), area under the concentration-time curve calculated to last measured concentration (AUClast), and extrapolated to infinity (AUCinf). PK parameters were determined using a non-compartmental analysis in WinNonlin. Results: Seventeen pts were enrolled; 9 with normal hepatic function and 8 with hepatic impairment. Niraparib Cmax was 7% lower in pts with moderate hepatic impairment compared with pts with normal hepatic function (Table). Overall exposure was increased in pts with moderate hepatic impairment, with niraparib AUClast and AUCinf increased 45% and 60%, respectively. Safety data during the PK phase of the study is consistent with the known profile for niraparib. Conclusions: Pts with moderate hepatic impairment experienced increased niraparib exposure which did not noticeably alter the toxicity profile in this population. Clinical trial information: NCT03359850. [Table: see text]

Population pharmacokinetics of PF-05280014 (a trastuzumab biosimilar) and reference trastuzumab (Herceptin®) in patients with HER2-positive metastatic breast cancer

Purpose

PF-05280014 is a biosimilar to trastuzumab (Herceptin^®). Following demonstration of pharmacokinetic (PK) similarity in healthy volunteers, a comparative clinical study in patients with HER2-positive metastatic breast cancer (mBC) compared the efficacy, safety and immunogenicity of PF-05280014 and trastuzumab sourced from the EU (trastuzumab-EU), both with paclitaxel.

Methods

Population PK of PF-05280014 and trastuzumab-EU was evaluated.

Results

Overall, 702 patients were treated: PF-05280014 (n = 349) and trastuzumab-EU (n = 353). Peak-and-trough serum drug concentration samples were collected (selected doses) following repeated intravenous administration of PF-05280014 or trastuzumab-EU. Population PK analysis was performed with drug concentration–time data to cycle 17 for each compound, using nonlinear mixed effect modeling. Potential baseline covariates (circulating HER2 concentrations, body weight, Japanese race, Eastern Cooperative Oncology Group status, number of metastatic sites and antidrug antibody status) were evaluated. Concentration–time data of PF-05280014 and trastuzumab-EU were adequately described by a two-compartment model with first-order elimination, with inter-individual variability (IIV) on clearance (CL), volumes of distribution in central compartment (V₁) and peripheral compartments, and intercompartment clearance. Similar estimated PK parameters and IIV were obtained for both treatments. For PF-05280014 and trastuzumab-EU, baseline body weight was an influential covariate on CL and V₁; the magnitude was comparable between treatments. PK was consistent between the limited number of Japanese and non-Japanese patients for both compounds.

Conclusions

PF-05280014 and trastuzumab-EU had similar PK parameters and influential PK covariates in patients with HER2-positive mBC. These results provided further evidence in patients for PK similarity between PF-05280014 and trastuzumab-EU.

Clinical trial registration

ClinicalTrials.gov, NCT01989676.

Abstract P4-21-19: Systematic review of clinical trials for monoclonal antibody biosimilars in HER2-positive breast cancer

Background: A number of proposed trastuzumab (TRAS) biosimilars are now in development for HER2-overexpressing breast cancer treatment. The purpose of this study was to systematically collate all published clinical data to assess the weight of available evidence for TRAS biosimilars in HER2-positive (+) breast cancer (BC), and to identify additional studies, not captured in the scientific literature, to support informed decision-making by healthcare stakeholders, as well as to raise awareness of ongoing developments within the field. Methods: MEDLINE®, Embase® and ISI Web of Science® were searched from inception to Sept 3, 2015. Conference proceedings (n=17) were searched from 2012 to Jul 31, 2015. Studies disclosing potential use of proposed biosimilars in the treatment of HER2+ BC were screened and categorized by originator and study type (English language only). To assess data strength and validity, risk of bias assessments were conducted. The ClinicalTrials.gov (CT.gov) registry was searched to identify any planned/ongoing/complete biosimilar trials in HER2+ BC. Results: On the analysis cut-off date, a total of 7 clinical studies (12 publications) were identified for proposed biosimilars of TRAS. The biosimilars identified for TRAS with published clinical data were BCD-022, CT-P6, FTMB and PF-05280014. For BCD-022, a pharmacokinetics (PK)/safety study in HER2+ BC (N=46) evaluating BCD-022 compared to TRAS, demonstrated equivalence between the two treatments. A PK/safety study (N=174) and comparative safety/efficacy study (N=475) of CT-P6 in HER2+ BC patients both provided evidence of PK equivalence, safety, and efficacy of the proposed biosimilar in this patient population. Bioequivalence of FTMB (versus TRAS) was also reported based on the results of a PK/safety study (N=118) in healthy subjects. For PF-05280014, a PK/safety study (N=105) in healthy volunteers demonstrated equivalence with TRAS. One published comparative safety/efficacy study protocol for PF-05280014 versus TRAS was identified for first-line treatment of patients with HER2+ BC (estimated [E]:N=690), and a second PK/efficacy/safety protocol for neoadjuvant BC treatment (E:N=220) was also published. A number of other planned studies were identified in CT.gov. These included 4 comparative safety/efficacy studies in HER2+ BC evaluating ABP 980 (E:N=808), CT-P6 (N=383/N=532), SB3 (E:N=806) and 2 PK/safety studies (BCD-022 [E:N=206], CT-P6 [E:N=174]) in women with BC. Two studies investigating PK and safety in healthy volunteers were also identified (PF-05280014 [E:N=162], SB3 [E:N=109]). Conclusions: This systematic review provides an unbiased synthesis of available evidence for proposed TRAS biosimilars in HER2+ BC, including data to support clinical similarity. The available clinical data for the 4 proposed biosimilars (BCD-022, CT-P6, FTMB and PF-05280014) investigated in a total of 918 healthy subjects or patients indicated highly comparable PK, safety, or efficacy profiles, versus TRAS. Additional data are required to fully evaluate the clinical similarity for proposed TRAS biosimilars, and the completion of several ongoing comparative trials are expected to provide further assurance of safety and efficacy in specific patient populations.

Citation Format: Jacobs I, Isakov L, Vana AM, Coiro J, Zacharchuk C, Ewesuedo R. Systematic review of clinical trials for monoclonal antibody biosimilars in HER2-positive breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-19.

Biosimilars for the Treatment of Cancer: A Systematic Review of Published Evidence

Background

Biologic treatments for cancer continue to place a significant economic burden on healthcare stakeholders. Biosimilar therapies may help reduce this burden through cost savings, thereby increasing patient access.

Objectives

The purpose of this study was to collate all published data to assess the weight of available evidence (quantity and quality) for proposed monoclonal antibody biosimilars and intended copies, for the treatment of cancer.

Methods

MEDLINE^®, Embase^®, and ISI Web of Science^® databases were searched to September 2015. Conference proceedings (17) were searched (2012 to July 2015). Searches of the United States National Library of Medicine ClinicalTrials.gov registry were also conducted. Risk of bias assessments were undertaken to assess data strength and validity.

Results

Proposed biosimilars were identified in 23 studies (36 publications) in oncology and ten studies in 14 publications in oncology and chronic inflammatory diseases for bevacizumab, rituximab, and trastuzumab originators. Based on our review of the included published studies, and as inferred from the conclusions of study authors, the identified proposed biosimilars exhibit close similarity to their originators. Published data were also retrieved on intended copies of rituximab. It remains unclear what role these agents may have, as publications on rigorous clinical studies are lacking for these molecules.

Conclusion

While biosimilar products have the potential to improve patient access to important biologic therapies, robust evidence of outcomes for monoclonal antibody biosimilars in treating cancer patients, including data from comparative efficacy and safety trials, is not yet available in the published literature. Significant data gaps exist, particularly for intended copies, which reinforces the need to maintain a clear differentiation between these molecules and true biosimilars. As more biosimilars become available for use, it will be important for stakeholders to understand fully the robustness of overall evidence used to demonstrate biosimilarity and gain regulatory approval.

Electronic supplementary material

The online version of this article (doi:10.1007/s40259-016-0207-0) contains supplementary material, which is available to authorized users.

Evaluating imbalances of adverse events during biosimilar development

Biosimilars are designed to be highly similar to approved or licensed (reference) biologics and are evaluated based on the totality of evidence from extensive analytical, nonclinical and clinical studies. As part of the stepwise approach recommended by regulatory agencies, the first step in the clinical evaluation of biosimilarity is to conduct a pharmacokinetics similarity study in which the potential biosimilar is compared with the reference product. In the context of biosimilar development, a pharmacokinetics similarity study is not necessarily designed for a comparative assessment of safety. Development of PF-05280014, a potential biosimilar to trastuzumab, illustrates how a numerical imbalance in an adverse event in a small pharmacokinetics study can raise questions on safety that may require additional clinical trials.

Abstract OT1-1-03: A phase 3 randomized, double-blind trial comparing PF-05280014 + paclitaxel vs. trastuzumab + paclitaxel for treatment of HER2+ metastatic breast cancer patients

Background: PF05280014 is being developed as a potential biosimilar to trastuzumab. PF-05280014 demonstrated similarity to trastuzumab in nonclinical evaluations. In a Phase I trial in healthy volunteers, PF-05280014 pharmacokinetic characteristics and safety profile were shown to be similar to those of trastuzumab. The goal of this Phase 3 trial is to demonstrate that the efficacy and safety of PF-05280014 + paclitaxel are similar to those of trastuzumab sourced from the EU (trastuzumab-EU) + paclitaxel in women with HER2-positive metastatic breast cancer.

Trial design: In this randomized, double-blind trial, patients will be randomized 1:1 into 2 arms: PF-05280014 + paclitaxel and trastuzumab-EU + paclitaxel. Randomization will be stratified by prior adjuvant trastuzumab exposure and estrogen receptor status. The order of infusion will be PF-05280014 or trastuzumab (4 mg/kg in Cycle 1; 2 mg/kg thereafter over 90 min) first followed by paclitaxel (80 mg/m2).

Eligibility: Female patients, aged ≥18 y with confirmed HER-2 overexpressing metastatic breast cancer, ≥1measurable lesion (RECIST), Eastern Cooperative Oncology Group status 0–2, normal left ventricular ejection fraction, and normal laboratory values are eligible. Key exclusion criteria are prior systemic therapy for metastatic disease, prior cumulative dose of anthracyclines &gt;400 mg/m2, and major surgery, radiotherapy or investigational agents within 4 weeks. All subjects must provide informed consent.

Aims: The primary objective is to demonstrate the similarity in objective response rate (ORR) of PF-05280014 + paclitaxel treatment to that of trastuzumab-EU + paclitaxel. Secondary objectives include evaluating 1-year progression-free survival, safety, pharmacokinetics, and immunogenicity of these combination treatments.

Statistical methods: This study tests whether the ORR of PF-05280014 is similar to that of trastuzumab-EU, using a margin of 13%, i.e., 5% alpha for non-inferiority. Assuming 60% ORR in both arms, 600 patients (300/arm) will be needed to achieve 90% power. Assuming 10% attrition, a total of 660 patients will be randomized. The intent-to-treat (ITT) population is defined as all subjects who are randomized to receive treatment. The per-protocol population is defined as all subjects who are randomized to and receive treatment and do not have any major protocol violations and will be used for evaluation efficacy endpoints.

Accrual: The target accrual of this global trial is 660 patients.

Contact information: For further information, please contact the Director, Clinical Trials Disclosure Group, Pfizer Inc. (marla.brickman@pfizer.com).

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT1-1-03.

Pharmacokinetic study of clofarabine: Oral bioavailability and the effect of cimetidine on renal clearance

e13074

Background: Clofarabine (CLO) is a purine analog with activity in myeloid neoplasms. Its oral dosing has been based on an estimated bioavailability (F) of 49% from uncontrolled trials. Animal models suggest that CLO renal clearance (CL) may be impaired in the presence of inhibitors of organic cation transporter-2 (OCT2), which mediates transport across the renal tubular basolateral membrane. We conducted a pharmacokinetic (PK) study of CLO to determine F, and examine the effect of the OCT2 inhibitor, cimetidine (CIM) on intravenous (IV) CLO. Methods: Patients had: 1) untreated AML ≥ 60 years of age unsuited for standard induction, 2) relapsed or refractory AML, or 3) MDS after failure of ≥ 1 prior regimen. Treatment was: CLO 15 mg/m2 IV day 1, CLO 30 mg/m2 orally (PO) day 3, CLO 15 mg/m2 IV day 5 preceded by two doses of oral CIM, and CLO 30 mg/m2 PO on days 6 and 7. PK studies were obtained after CLO dosing on days 1, 3 and 5. For each dose, CLO plasma concentration was determined, and concentration-time data was analyzed by non-compartmental methods. F was determined for each patient. The geometric means of area under the curve (AUC), 0-∞, and CL for IV CLO administered after CIM doses were compared with AUC and CL for IV CLO administered without CIM. Results: Interim data for the first ten treated patients, with comparisons of PK parameters are shown in the table below. Conclusions: Using patients as their own controls, F of CLO is higher than previously estimated. AUC of CLO is increased and CL is decreased in the presence of CIM, likely owing to inhibition of OCT2-mediated renal tubular secretion. This study is the first human trial to suggest that CLO CL may be impaired in the presence of OCT2 inhibitors, such as cimetidine, trimethoprim, verapamil and nicotine. [Table: see text]

A first-in-human, phase I safety and pharmacokinetic study of genz-644282, a non-camptothecin topoisomerase I inhibitor, in patients with advanced solid tumors

2534

Background: The approved topoisomerase I (TopI) inhibitors (irinotecan and topotecan) are camptothecin derivatives. The lactone ring structure of camptothecins negatively impacts their clinical potential.Genz-644282 is a novel non-camptothecin that induces TopI-DNA cleavage complexes at similar as well as unique genomic positions; that are more persistent. This study was designed using a pharmacokinetic-pharmacodynamic (PK-PD) model to predict the maximum tolerated dose (MTD). Methods: A PK-PD relationship of Genz-644282 to inhibit tumor growth was derived (Simeoni, Can Res 2004). Using an accelerated titration design, cohorts of 1, 3 or 6 patients received 3 weekly doses of Genz-644282 on a 28 day schedule starting with 0.5 mg/m2. After MTD on the 28 day schedule was exceeded, 21 day schedule was initiated. Results: 49 patients (N=44 data available: 26M :18F) were dosed. Tumor types were colorectal (15), breast (5), small cell lung (SCLC 3), non-small cell lung (4), others (17). As predicted from the PK-PD model 8 cohorts were evaluated on the 28 day schedule before defining the MTD. The MTD was 8 mg/m2 and 9 mg/m2 for the 28 day and 21 day schedules, respectively. Dose limiting toxicities that determined the MTD were: gr 4 thrombocytopenia (n=2); gr 2 thrombocytopenia (n=1) and gr 4 neutropenia (n=1) both of which resulted in ≥72h delays in initiating cycle 2. Treatment emergent adverse events (>10%) were nausea (45%), fatigue (39%), anorexia (32%), anemia (27%), vomiting (23%), thrombocytopenia (18%), diarrhea (16%), dehydration (16%), hyperglycemia (16%), cough (16%), dyspnea (14%), depression (11%) and hyponatremia (11%). Efficacy data suggest 2 responders with SCLC (1 minor response;1 complete response), and 2 patients (breast, gastric) with stable disease (≥ 6 months). PK data show a Genz-644282 half-life of approximately 50 h, a linear dose-exposure relationship, and no accumulation in between doses. Conclusions: Genz-644282 is a non-camptothecin TopI inhibitor in phase I development with ongoing expansion phase. The emerging pk, efficacy and safety data are suggestive of a distinct clinical profile of Genz-644282 from the camptothecins.

Abstract 750: Impairment of clofarabine (CLO) clearance (CL) in the presence of cimetidine: Evidence of a drug-drug interaction between clofarabine and inhibitors of human organic cation transporter-2 (hOCT2)

Background: CLO is a nucleoside analog with efficacy in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). Preclinical studies using an isolated, perfused rat-kidney model suggested that CLO may be a substrate of OCT2, a channel that mediates the transport of cations across the renal tubular basolateral membrane. Evidence of this mechanism is lacking in humans, though this property could contribute to drug interactions with compounds such as cimetidine that inhibit hOCT2. Methods: Eligible patients were: 1) untreated AML ≤ 60 years of age unsuited for intensive induction therapies, 2) relapsed or refractory AML, or 3) MDS patients who failed ≤ 1 prior regimen. Patients were treated with CLO according to the schedule: CLO 15 mg/m2 IV day 1, CLO 30 mg/m2 PO day 3, CLO 15 mg/m2 IV day 5 preceded by two doses of oral cimetidine (800 mg PO 8-10 hours apart), and CLO 30 mg/m2 PO on days 6 and 7. Pharmacokinetic (PK) studies were obtained after CLO dosing on days 1, 3 and 5. CLO plasma concentration was determined, and concentration-time data was analyzed by non-compartmental methods. Oral bioavailability (F) was determined for each patient. The geometric means of area under the curve, 0-infinity (AUC), and CL for intravenous CLO administered after cimetidine doses were compared with AUC and CL for intravenous CLO administered without cimetidine. Results: To date, 8 patients have been treated. Mean F = 0.66, 90% confidence interval (CI) (0.49, 0.87). Comparisons of PK parameters between IV dosing with and without cimetidine are shown in the table. Conclusions: Co-administration of the hOCT2 inhibitor cimetidine with CLO appears to increase CLO AUC by impairing renal CL. Enrollment continues in an attempt to further support the putative mechanism of CLO renal clearance by hOCT2-mediated tubular secretion, and to further investigate the clinical import of this drug-drug interaction.

Phase I evaluation of AZD2171, a highly potent and selective inhibitor of VEGFR signaling, in combination with selected chemotherapy regimens in patients with advanced solid tumors

3034

Background: AZD2171 is an oral, potent, selective inhibitor of vascular endothelial growth factor receptor (VEGFR). Trials have demonstrated that inhibition of the VEGF pathway, in combination with certain chemotherapy, provides benefit to patients with a broad range of solid tumors. Methods: This Phase I trial was conducted in heavily pretreated solid tumor patients. In a single protocol, escalating doses of AZD2171 were evaluated (20, 30 and 45 mg) in combination with four separate chemotherapy regimens: mFOLFOX6 (oxaliplatin 85 mg/m2; 5-FU 400 mg/m2; leucovorin 400 mg/m2 q2 weeks; Arm 1); irinotecan 300 mg/m2 q3 week (Arm 2); docetaxel 75 mg/m2 (Arm 3) and pemetrexed 500 mg/m2 (Arm 4). The primary objective was to evaluate safety and tolerability of the combinations and secondary objective to evaluate pharmacokinetic (PK) interaction and clinical efficacy. Maximum tolerated dose (MTD) toxicity was defined through two cycles. Results: 46 patients have been enrolled: 28/35 evaluable for efficacy/toxicity. The MTD has been reached in two arms: Arm 2 - 20 mg AZD2171 and Arm 4 - 30 mg AZD2171. Arm 3 enrollment continues at 45 mg AZD2171. Two dose-limiting toxicities (DLTs) were observed in eight patients at 30 mg AZD2171 in Arm 1. Enrollment of an additional cohort of less heavily pre-treated patients is ongoing to determine the tolerability of 30 mg AZD2171 with FOLFOX. DLTs have included grade 3 fatigue in Arms 1, 2 & 4; grade 3 diarrhea in Arm 1; grade 3 hand-foot syndrome & grade 4 neutropenic fever in Arm 2; and grade 3 hypertension in Arm 4. AZD2171 did not appear to have a major effect on the PK profile of any chemotherapy regimen tested. Steady-state values are comparable with AZD2171 monotherapy. There have been 13 responses (minor response, n=5; partial response, n=6; complete response, n=2; stable disease ≥ 4 cycles, n=6) in heavily pretreated patients, some having demonstrated resistance to identical chemotherapies. Duration of response has been impressive (4-22+ cycles). Conclusions: AZD2171 combinations have been well tolerated with expected toxicities and encouraging responses.

[Table: see text]

O6-methylguanine-DNA methyltransferase activity and promoter methylation status in pediatric rhabdomyosarcoma

OBJECTIVES

To determine the activity of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) and MGMT promoter methylation status of pediatric rhabdomyosarcoma (RMS) and examine MGMT in RMS tumors from different prognostic groups.

METHODS

Fifteen samples each of the alveolar (ARMS) and embryonal (ERMS) subtypes were obtained for analysis of MGMT activity and promoter methylation status. MGMT activity was assayed by measuring the removal of O6-[3H] methylguanine from [3H]-methylated substrate by a tumor extract containing the enzyme. Promoter methylation status was examined using methylation-specific polymerase chain reaction (PCR).

RESULTS

MGMT activity was successfully assayed from 25 samples, 10 ERMS and 15 ARMS. All ERMS and 11 of the 15 ARMS samples displayed high activity levels. There was significant intertumor variability among both subtypes but no significant difference in mean activity between the two histologic groups. There were trends toward increased activity in ERMS tumors and tumors from anatomically unfavorable locations. Only one tumor was hypermethylated at the MGMT promoter region.

CONCLUSIONS

This analysis suggests that a low percentage of RMS samples are hypermethylated at the MGMT promoter and that most have significant MGMT activity, implying that clinical trials with MGMT-modulating agents may have a role in the treatment of these tumors. This analysis does not support MGMT activity as an explanation of the differential response to chemotherapy demonstrated by ARMS and ERMS, but does suggest that MGMT may be involved in RMS treatment failure regardless of subtype and in the poorer response shown by tumors from unfavorable locations.

Influence of some dopaminergic agents on antinociception produced by quinine in mice

1. The analgesic effect of quinine and the influence of some dopaminergic agents on it were studied in mice. 2. Quinine (25-130mg/kg, ip) effectively elicited antinociceptive effect in a dose related manner. 3. D-Amphetamine (2.5-4mg/kg, ip), L-dopa (25mg/kg, sc), L-dopa (25mg/kg, sc) plus benserazide (12.5mg/kg, sc), alpha-methyl-p-tyrosine (50mg/kg, ip) plus L-dopa (25mg/kg, sc) and pargyline (50mg/kg, ip) significantly attenuated the antinociceptive effect of quinine (50mg/kg, ip), while DOPS (4mg/kg, ip) did not affect quinine antinociception. 4. Pimozide (4mg/kg, ip), L-sulpiride (40mg/kg, ip), SCH 23390 (0.2mg/kg, sc) and alpha-methyl-p-tyrosine (50mg/kg, ip) effectively potentiated the antinociceptive effects of quinine (50mg/kg, ip). 5. Pimozide (4mg/kg, ip) also antagonised the antagonistic effect of d-amphetamine (4mg/kg, ip) on the antinociceptive effect of quinine (50mg/kg, ip). 6. These data indicate that quinine elicited antinociception dose dependently. Furthermore, the influence of pimozide, L-sulpiride and SCH 23390 on quinine antinociception suggests the involvement of dopaminergic mechanisms.