Abstract OT2-07-07: ATR inhibitor M6620 (formerly VX-970) with cisplatin in metastatic triple-negative breast cancer: Preliminary results from a phase 1 dose expansion cohort (NCT02157792)

Background: ATR is a critical regulator of the cellular response to replication stress; it signals DNA damage repair, mediated through homologous recombination. Many cancers depend on ATR to survive DNA damage. M6620 is a potent, selective inhibitor of ATR that augments the anticancer activity of cisplatin in preclinical triple-negative breast cancer (TNBC) models. Given the high prevalence of TP53 mutations in TNBC and limited platinum responsiveness in patients lacking a BRCA1/2 mutation, this study was designed to evaluate the safety and efficacy of M6620 in combination with cisplatin in an expansion cohort of patients with BRCA1/2 wild-type advanced/metastatic TNBC.

Methods: Eligible patients had advanced/metastatic ER-, PR-, and HER2- breast cancer with 0-2 prior non–platinum-based therapies and measurable disease per RECIST 1.1. First line patients were eligible if relapse occurred ≥3 months after prior (neo)adjuvant chemotherapy. Of a maximum 50 patients planned for enrollment, ≥30 were required to have BRCA1/2 germline wild-type status and basaloid molecular subtype tumors on central testing. Patients received intravenous cisplatin 75 mg/m2 on day 1 with intravenous M6620 140 mg/m2 on days 2 and 9 of each 21-day cycle. In patients intolerant of cisplatin or at investigator's discretion, cisplatin could be switched to carboplatin AUC 5 with M6620 90 mg/m2.

Results: At the time of abstract submission, 35 female patients were enrolled in this study; 18 patients with confirmed BRCA1/2 wild-type and basaloid metastatic TNBC who received ≥1 cycle of study drug and had ≥1 baseline scan and ≥1 on-treatment scan at the time of the data cut were included in the primary efficacy analysis. Median progression-free survival (PFS) was 4.1 months (90% CI, 1.6-6.9 months). PFS was ≥ 6 months in 2 patients and ≥ 3 months in 8 patients. Preliminary unconfirmed objective response [complete response or partial response (PR)] was observed in 38.9% (90% CI, 19.9%-60.8%) of patients. All 7 patients with preliminary objective response had PR as best overall response; the longest duration of response was 183 days. Response was ongoing in 4 patients with PR at the time of data cutoff. Grade ≥3 related treatment-emergent adverse events occurred in 16 of 35 patients: neutropenia (n=8), anemia (n=5), vomiting (n=4), nausea (n=3), and, in 1 patient each, thrombocytopenia, neutrophil count decreased, platelet count decreased, hypokalemia, generalized weakness, rigors, and acute kidney injury.

Conclusions: Combination of M6620 and cisplatin shows encouraging antitumor activity and tolerability in patients with advanced/metastatic TNBC. The study is ongoing; updated safety and efficacy results will be presented.

Citation Format: Telli ML, Lord S, Dean E, Abramson V, Arkenau H-T, Murias C, Becerra C, Tang R, Penney MS, Pollard J, Conboy G, Fields SZ, Shapiro G, Tolaney SM. ATR inhibitor M6620 (formerly VX-970) with cisplatin in metastatic triple-negative breast cancer: Preliminary results from a phase 1 dose expansion cohort (NCT02157792) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-07-07.

Abstract P5-06-05: Preclinical characterization of VX-984, a selective DNA-dependent protein kinase (DNA-PK) inhibitor in combination with doxorubicin in breast and ovarian cancers

Background: The efficacy of chemotherapeutic agents such as doxorubicin, which cause lethal DNA double-strand breaks (DSBs), is diminished by efficient repair of the damaged DNA in cancer cells. DNA-PK is a key regulator of the non-homologous end joining (NHEJ) pathway, which is responsible for repairing DSBs. Studies of nonselective inhibitors of DNA-PK have shown that cancer cells depend on DNA-PK for survival following treatment with DSB-inducing agents. However, a comprehensive characterization of DNA-PK inhibition has been hampered by a lack of selective inhibitors. Here we describe VX-984, a potent and selective inhibitor of DNA-PK, and its preclinical profile in combination with doxorubicin both in vitro and in vivo.

Methods: VX-984 was examined as a single agent and in combination with doxorubicin or pegylated liposomal doxorubicin (PLD) in a panel of breast cancer cell lines and in mouse xenograft models, respectively.

Results: In vitro, inhibition of DNA-PK by VX-984 enhanced the cytotoxic activity of doxorubicin in established breast cancer cell lines and in primary ovarian tumor explants. Notably, mean Bliss DE >10% (strong synergy) were observed for doxorubicin in the presence of VX-984 in 22 of 35 breast cancer cell lines and 21 of 44 ovarian cancer cell lines in a broad cancer cell line screen. Further, the efficacy observed with VX-984 was associated with increased DNA damage as measured by phosphorylated histone H2AX (gamma-H2AX) and phosphorylated Kruppel-associated protein (pKAP1) in DU4475, MDA-MB-436 and MDA-MB-468 breast cancer cell lines, which is consistent with diminished DSB repair. In vivo, VX-984 significantly enhanced the efficacy of PLD in ovarian cancer patient-derived xenograft models and in cell line xenograft models.

Conclusions: These data provide evidence that inhibition of DNA-PK by VX-984 enhances the efficacy of doxorubicin in preclinical models and support the use of VX-984 in combination with DSB agents such as anthracyclines including PLD for the treatment of breast and ovarian cancers. VX-984 is currently in a Phase 1 clinical trial in combination with PLD.

Sponsored by Vertex Pharmaceuticals Incorporated.

Citation Format: Boucher D, Newsome D, Takemoto D, Hillier S, Wang Y, Arimoto R, Maxwell J, Charifson P, Fields SZ, Tanner K, Penney MS. Preclinical characterization of VX-984, a selective DNA-dependent protein kinase (DNA-PK) inhibitor in combination with doxorubicin in breast and ovarian cancers [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 P5-06-05.

Abstract P6-07-31: Assessing germline Homologous Recombination pathway deficiency in BRCA1 mutation carriers using Single Cell Network Profiling

Background: Inherited alterations in BRCA1/2 genes increase genomic instability and cancer susceptibility. DNA sequencing detects BRCA1/2 mutations, but has the following limitations; 1) mutations may have unknown functional significance, 2) epigenetic alterations and mutations in other Homologous Recombination (HR) pathway components are not detected, and 3) the combined effects of pathway mutations are not understood. Thus a functional assessment of HR competence at the single cell level remains an unmet need as BRCA1/2 sequencing does not holistically inform on functionality of the HR pathway. Single Cell Network Profiling (SCNP) is a multiparametric flow cytometry-based assay that simultaneously measures, at the single cell level, extracellular surface markers and functional changes in intracellular signaling in response to extracellular modulators (Kornblau et al. Clin Cancer Res 2010). In this study, we tested the ability of SCNP to detect and quantify functional changes in HR signaling using peripheral blood mononuclear cell (PBMC) samples from BRCA1 mutation carriers (MUT) and wild type (WT) subjects.

Methods: HR pathway activity was examined in PBMCs from BRCA1 MUT (n = 21) or WT (n = 20) subjects. Cell lines carrying BRCA1 MUTor WT genes were used as controls. PBMCs were stimulated with anti-CD3 and anti-CD28 for 24 hours to induce T cell proliferation then treated with PARP inhibitor (PARPi) AZD2281 +/− Temozolomide (TMZ) for 48h or 72h to induce DNA damage. DNA damage response (DDR) readouts were measured in both CyclinA2- and CyclinA2+ T cell subsets. Measurements included induced levels of p21, p53 and phosphorylation (p−) of p-H2AX, p-DNA-PKcs, p-RPA2/32, and p-BRCA1.

Results: As expected based on the mechanism of action of PARPi, higher levels of induced p-H2AX and p53 were observed in CyclinA2+ cells of BRCA1 MUT versus WT cell line controls. In PBMCs, T cell proliferation (%CyclinA2+) was positively associated with PARPi induced DDR readouts. After controlling for proliferation, statistically significant differences in PARPi induced DDR signaling were observed between BRCA1 MUT and WT samples in many simultaneously assessed readouts including p-H2AX, p53 and p21 (increased in MUT), particularly in CyclinA2+ cells. Additionally, BRCA1 MUT samples displayed lower basal p-BRCA1 but higher induced p-BRCA1 levels compared to BRCA1 WT samples.

Conclusions: SCNP was able to detect and quantify functional differences between PBMC samples from BRCA1 MUT (haploinsufficient) and WT donors by quantitatively assessing DDR signaling in CyclinA2+ T cells. Once verified on a larger data set, the assay could form the basis for the development of screening tests to identify subjects at higher risk of developing cancer or stratification tests to inform on cancer patient selection for treatment with PARP inhibitors.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-07-31.

Clinical and pharmacokinetic (PK) findings in a phase I study of 7-t-butyldimethylsilyl-10-hydroxycamptothecin (AR-67) in patients with refractory solid tumors

2534

Background: AR-67 is a 3rd generation camptothecin analog selected for development based on the high in vitro stability of its pharmacologically active lactone form and high potency in preclinical models. This report describes the initial phase I study of intravenous AR-67 in adults with refractory solid tumors. Methods: AR-67 was infused over 1 hour for 5 days of a 21-day cycle using an accelerated titration phase I trial design. PK was performed on the 1st and 4th day of cycle 1. AR-67 was assayed with a validated chromatography method. Toxicity and response were assessed using NCI CTC (v3) grading scale and RECIST. Results: In total, 26 patients were treated at 9 dose levels (mg/m2/day): 1.2 (n=2), 1.67 (n=3), 2.34 (n=3), 3.2 (n=3); 4.5 (n=1), 6.3 (n=1), 7.5 (n=7), 8.9 (n=4) and 12.4 (n=2). Median age 62 (range 31–79), 15M/11F, median prior therapies 3 (range 1 to 6). Tumor types included: colorectal (8), non-small cell lung (NSCLC) (4), small cell lung (3), soft tissue sarcoma, (3), head and neck (2), prostate (2), and other (4). 21 subjects completed 2 or more cycles of therapy, 5 subjects received 1 cycle of therapy and had rapid disease progression (1 received 2d of drug prior to PD), 1 subject is still under treatment after 9 cycles. DLTs were observed in 5 patients: 2 of 2 at 12.4 mg/m2/day (Gr 4 febrile neutropenia, Gr 3 fatigue); 2 of 4 at 8.9 mg/m2/day (Gr 4 thrombocytopenia), 1 of 7 at 7.5 mg/m2/day (Gr 4 thrombocytopenia). Common C1 worst-grade drug related toxicities (CTC I/II % vs III/IV %): Hg (27/8), WBC (11/19), ANC (19/8), platelets (19/12), fatigue (15/8) insomnia (8/0), flushing (15//0), constipation (8/0), nausea (23/0), ALT elevation (12/0), hiccups (8/0). Antitumor activity, assessed by development of PR and SD, was observed in NSCLC, SCLC, colon and bladder cancer. The lactone form was predominant in plasma (>85% of AUC) at all time points. Clearance was constant with increasing dose and exposure (AUC) correlated with toxicity. Conclusions: AR-67 has superior lactone stability compared to approved analogs, has a predictable toxicity profile that did not include diarrhea and has activity in NSCLC. The RP2D is 7.5 mg/m2/day for 5 days of a 21-day cycle. This work was supported by R21-CA-123867 and Arno Therapeutics.

[Table: see text]

Pharmacokinetics (PK) of the highly lipophilic and blood stable camptothecin AR-67 (7-t-butyldimethylsilyl-10- hydroxycamptothecin) in adult patients with solid malignancies

2546

Background: Camptothecin analogs possess a labile lactone ring, which readily undergoes a pH dependent, albeit reversible, hydrolysis in plasma to yield a carboxylate moiety. The latter is considered inactive due to its electronegative charge that impedes transport into cells. Furthermore, the carboxylate is cleared rapidly and causes toxicity in eliminating organs due to lactonation. AR-67 is a highly lipophilic 3rd generation analog with superior stability of its lactone form in preclinical models. This report describes the PK of AR-67 in patients with refractory solid tumors enrolled in a phase I study. Methods: AR-67 was infused over 1 hr for 5 days every 21-days. PK was performed on the 1st and 4th day of cycle 1. Blood, plasma, and urine were collected (0–24 hrs) from 26 patients (see 09-AB-30336-ASCOAM) treated at 9 dose levels: 1.2–12.4 (mg/m2/day). AR-67 carboxylate and lactone were assayed with a validated chromatography method. Results: AR-67 was detectable at all dose levels. Blood concentrations mirrored those in plasma and were superimposable when adjusted by the hematocrit. AR-67 concentration peaked at the end of the 1-hr infusion and declined biexponentially with a terminal t1/2 of 1.4 hr (plasma lactone). A linear relationship was observed between dose and AUC. The lactone clearance on Day 1 was 16.6 (±5.5) vs. 19.6 (±6.3) L/hr/m2 on Day 5. The carboxylate clearance was ∼ 6-fold higher. Lactone was the major form in all samples and its area under the time vs. concentration curve (AUC) was 85.5% (range 74.0%-94.1%) of the total AUC. Urine (0–24 hr) contained 2.5% (0.3%-6.7%) of the dose on Day 1 vs. 2.7% (0.9–11.1%) on Day 4. Extensive metabolite peaks were not observed in plasma, blood, or urine samples. Plasma protein binding of the carboxylate was 90% (range 80%-96%) vs. 95% (range 90%-98%) for the lactone. Conclusions: AR-67 is a lipophilic camptothecin with a unique PK profile. Unlike other clinically approved analogs with lower lactone stability (35%-65%), over 85% of the AR-67 AUC is in the active lactone form. This high lactone-low carboxylate exposure coupled with the apparently limited metabolism of AR-67 may result in increased activity and decreased toxicity.

[Table: see text]

Phase II study of eribulin mesylate (E7389) halichondrin b analog in patients with refractory breast cancer

1034

Background: Eribulin is a structurally simplified analog of halichondrin B, which inhibits microtubule dynamics via a novel mechanism characterized by suppression of microtubule growth, lack of effect on microtubule depolymerization, and sequestration of tubulin into nonfunctional aggregates. This study was designed to assess the activity and tolerance of eribulin in chemotherapy refractory patients with advanced breast cancer. Methods: Eribulin was evaluated in a single-arm Phase II trial in female patients with refractory breast cancer, ECOG performance status of 0–1, measurable disease, and neuropathy ≤ Grade 2. Patients received ≥ 1 prior chemotherapy regimen, including an anthracycline and a taxane. Eribulin was administered as a 2–5 min IV bolus of 1.4 mg/m2 on Days 1, 8, and 15 of a 28-Day cycle (Group 1). The schedule was modified to Days 1 and 8 of a 21-Day cycle (Group 2), because of dose delays. The primary efficacy endpoint was ORR according to RECIST criteria based upon independent review (IR) of tumor assessment. Results: Of 104 patients enrolled, 103 received eribulin treatment: 70 in Group 1, 33 in Group 2. Median age was 55 yrs (range 32–84). Patients had received a median of 4 prior chemotherapy regimens (range 1–11). Sixty-one percent of tumors were ER+, 14% Her2/neu 3+, and 29% were triple (ER, PR, Her-2) negative. The incidence of dose interruption, delay, or omission during Cycle 1 was 63% (Group 1) and 18% (Group 2). The most common drug related toxicities were neutropenia (75%, Grades 3: 31%, Grade 4: 30%, febrile neutropenia: 3.9%), fatigue (52%, Grade 3: 2.9%, no Grade 4), alopecia (Grade 1/2: 41%), nausea (37%, Grade 3: 1%, no Grade 4), and anemia (36%, Grade 3: 1%, no Grade 4). Peripheral neuropathy occurred in 34% of patients (Grade 3: 3.9%, no Grade 4). Best overall response rate (all PR) by IR was 14.5% and 15.2% in Groups 1 and 2, respectively; the combined ORR was 14.7% (95 % CI: 9–23%). Median PFS was 85 days, and the 6 mo PFS rate was 31%. Conclusions: Eribulin given as a 2–5 min IV infusion on Days 1, 8 of a 21-Day cycle or Days 1, 8, 15 of a 28-Day cycle exhibited a 15% PR rate by IR and a low incidence of Grade 3 neuropathy in this heavily chemotherapy pretreated population. The most common toxicity was neutropenia. The 21-Day schedule had an acceptable toxicity profile.

No significant financial relationships to disclose.

Phase II study of eribulin mesylate (E7389), a mechanistically novel inhibitor of microtubule dynamics, in patients with advanced non-small cell lung cancer (NSCLC)

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Background: Eribulin is a structurally-simplified, fully synthetic analog of the marine sponge natural product halichondrin B. Eribulin inhibits microtubule dynamics via a mechanistically novel mode of action. Methods: An open-label, single-arm, Phase II study of eribulin was conducted in patients with advanced NSCLC (ECOG of 0 or 1) who were treated with platinum-based doublet chemotherapy and stratified by prior taxane exposure. A total of 103 patients (83 with prior taxanes and 20 taxane naïve) were treated with eribulin (1.4 mg/m2), administered as a bolus infusion over 2 –5 minutes on Days 1, 8, and 15 of a 28-day cycle (N=77). Due to delays or skipped doses secondary to myelosuppression at Day 15 with recovery by Day 21, the protocol was amended to a schedule of Days 1 and 8 of a 21-day cycle (N=26). The primary efficacy endpoint was objective response rate. Independent radiologic review was used to confirm responses. Results: Of 106 enrolled patients, 103 received eribulin. Median age was 65 years and median number of prior therapies was 2, including taxanes (81%), gemcitabine (40%), pemetrexed (23%), and EGFR inhibitors (34%). Median number of cycles administered was 3 (range 1–15). Drug related toxicities included neutropenia grade 3 (23%) and 4 (26%), febrile neutropenia (4%), grade 3 fatigue (11%), grade 3 nausea (2%), and peripheral neuropathy grade 1/2 (37%) and 3 (2%). Based on RECIST criteria, the overall response rate (all partial responses) was 9.7% (95% CI: 4.0–15.4 %), with 10.8% PR in taxane pre-treated, and 5% PR in taxane naïve patients. Overall disease control rate (PR + SD) was 55.3%. 12-week progression free survival (PFS) rate was 53.0% (95% CI: 42.6–63.3%) and median PFS was 102 days (range 1–408+). Median duration of response was 176 days (range 50–291+), and median overall survival was 287 days (range 16–423+). The one year survival rate was 46.4% (95% CI: 34.9–58.0%). Conclusions: In this group of NSCLC patients who were treated with a median of two prior therapies, consisting in the majority of cases of two cytotoxic regimens, eribulin demonstrated an overall PR rate of 9.7% (10.8% in the taxane pre-treated) and 9.6 months median survival.

No significant financial relationships to disclose.

E7389, a novel anti-tubulin, in patients with refractory breast cancer

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Background: E7389 is a synthetic analog of halichondrin B, with a broad anti- proliferative activity against tumor cells. Methods: E7389 was evaluated in an open-label, single-arm Phase II trial as monotherapy for patients with refractory breast cancer (≥2 prior chemotherapy regimens, which must have included an anthracycline and a taxane). E7389 was administered as an IV bolus of 1.4 mg/m2 on Days 1, 8, and 15 of a 28-day cycle (group 1), or on Days 1 and 8 of a 21-day cycle (group 2). The primary efficacy endpoint was ORR. Results: As of 9 December 2005, 88 patients had received treatment, 68 in group 1 and 20 in group 2. Median age was 55 yrs (range 36–84) and ECOG performance status 0–1. Sixty-six percent of the tumors were ductal carcinomas, 6% lobular, and 27% were unclassified. Sixty percent of the tumors were ER+, 47% PR+, and 17% Her2/neu 3+. The patients had received at least two previous regimens, with a median number of 5 (range 2–14). Forty-eight percent of the patients had also used hormonal therapy. Forty-nine patients in group 1 and 12 patients in group 2 had completed their 2nd cycle of treatment, and twenty-one in group1 and 1 in group 2 their 4th cycle. Safety: The major toxicity related to study drug was neutropenia. Among 73 patients with preliminary safety data available, two patients had Grade 3 febrile neutropenia, and 31 had Grade 3 or 4 neutropenia or leukopenia. The other Grade 3 toxicities encountered in more than two patients were dehydration (4 patients) and dyspnea (4 patients). Grade 3 peripheral neuropathy was reported in 2 patients. Efficacy: At the end of cycle four there were 10 (15.2%) confirmed partial responses (PRs) out of 66 evaluable patients in group 1, and 1 confirmed PR (5.6%) out of 18 evaluable patients in group 2. The median duration of confirmed responses was 113 days. Conclusions: Based on the safety and efficacy in this refractory breast cancer population, E7389 appears to be a therapy worthy of continued investigation in patients with heavily pretreated breast cancer. In order to comply with the current demand for individualized cancer care, bio-markers which would predict the sensitivity to E7389 are being searched in the tumor samples of the patients in the current and forthcoming studies.

[Table: see text]

Preliminary results of combined therapy with topotecan and carboplatin in advanced non-small-cell lung cancer

Topotecan is a topoisomerase I inhibitor and an analogue of camptothecin with demonstrated activity in small-cell lung cancer. However, less is known about the potential role of topotecan in advanced non-small-cell lung cancer (NSCLC). Platinum-based combination therapy is currently recommended in NSCLC patients presenting with good performance status. Because topotecan demonstrates a novel mechanism of action, its investigation in platinum combinations is warranted. In phase I/II trials of topotecan given as part of a cisplatin-based regimen, significant antitumor activity has been observed, providing the rationale for conducting further studies aimed at assessing survival benefit. However, this combination exhibits sequence dependence, with increasing hematologic toxicity observed when cisplatin is administered on day 1 of a 5-day topotecan course. Cisplatin has been associated with dose-limiting nonhematologic toxicities. Carboplatin exhibits a different toxicity profile compared with cisplatin, which makes it an attractive agent to study in combination. A hypothesis can be made that carboplatin in combination with newer agents such as topotecan might compare favorably with classic cisplatin-based regimens, particularly with respect to efficacy:toxicity ratio. Therefore, a phase II study was initiated to determine the efficacy, toxicity, and safety of carboplatin-topotecan combination in advanced NSCLC. Preliminary results reported here show that topotecan with carboplatin is generally well tolerated with manageable hematologic toxicity. Indirect comparison with cisplatin-topotecan combination suggests a lower incidence of dose-limiting nonhematologic toxicity. Whether or not the carboplatin-topotecan regimen is able to offer tumor response and survival benefit comparable to those observed with cisplatin-based combinations remains to be established.

A randomised trial of oral versus intravenous topotecan in patients with relapsed epithelial ovarian cancer

A multicentre, randomised study was carried out in Europe, South Africa and North America to compare the activity and tolerability of oral versus intravenous (i.v.) topotecan in patients with relapsed epithelial ovarian cancer. Patients who had failed first-line therapy after one platinum-based regimen, which could have included a taxane, were randomised to treatment with either oral (p.o.) topotecan, 2.3 mg/m(2)/day or i.v. topotecan 1.5 mg/m(2)/day for 5 days every 21 days. Patients were stratified by prior paclitaxel exposure, interval from previous platinum therapy and tumour diameter. 266 patients were randomised. Response rates were 13% orally (p.o.) and 20% (i.v.) with a complete response in 2 and 4 patients, respectively. The difference in the response rates was not statistically significant. Median survival was 51 weeks (p.o.) and 58 weeks (i.v.) with a risk ratio of death (p.o. to i.v. treatment) of 1.361 (95% confidence interval (CI): 1.001, 1.850). Median time to progression was 13 weeks (p.o.) and 17 weeks (i.v.). The principal toxicity was myelosuppression although grade 3/4 neutropenia occurred less frequently in those receiving oral topotecan. Toxicity was non-cumulative and infectious complications were relatively infrequent. Non-haematological toxicity was generally mild or moderate. The incidence of grade 3/4 gastrointestinal events was slightly higher for oral than i.v. topotecan. Oral topotecan shows activity in second-line ovarian cancer and neutropenia may be less frequent than with the i.v. formulation. A small, but statistically significant, difference in survival favoured the i.v. formulation, but the clinical significance of this needs to be interpreted in the context of second-line palliative treatment. Oral topotecan is convenient and well tolerated and further studies to clarify its role are ongoing.

Oral topotecan as single-agent second-line chemotherapy in patients with advanced ovarian cancer

PURPOSE

To evaluate oral topotecan as single-agent, second-line therapy in patients with ovarian cancer previously treated with a platinum-based regimen.

PATIENTS AND METHODS

Patients (N = 116) received oral topotecan 2.3 mg/m2 daily for 5 days every 21 days. Eligibility criteria included histologic diagnosis of International Federation of Gynecology and Obstetrics stage III or IV epithelial ovarian cancer, bidimensionally measurable disease, prior platinum-containing chemotherapy, age > or = 18 years, performance status < or = 2, and life expectancy > or = 12 weeks.

RESULTS

Overall response rate was 21.6% (25 of 116 patients). Median duration of response was 25.0 weeks; median time to response was 8.4 weeks. Median time to progression was 14.1 weeks; median survival was 62.2 weeks. Grade 4 neutropenia was experienced by 50.4% of patients in 13.4% of courses administered. Grade 4 thrombocytopenia was experienced by 22.1% of patients in 5.1% of courses. Grade 3 or 4 anemia was experienced by 29.2% of patients in 8.5% of courses. Most frequent nonhematologic toxicities were predominantly (> 90%) grade 1 or 2 and included nausea, alopecia, diarrhea, and vomiting.

CONCLUSION

Second-line oral topotecan administered at 2.3 mg/m2 for 5 days every 21 days demonstrated activity in patients with progressive or recurrent ovarian cancer after first-line platinum-based chemotherapy. This activity was comparable to that seen in previous studies with intravenous topotecan. Grade 4 neutropenia was less frequent with oral topotecan than previously reported for intravenous topotecan. Oral topotecan is an active, tolerable, and convenient formulation of an established agent for the second-line treatment of advanced epithelial ovarian cancer and may also facilitate exploring prolonged treatment schedules.

Clinical evidence for topotecan-paclitaxel non--cross-resistance in ovarian cancer

PURPOSE

A large, randomized study comparing the efficacy and safety of topotecan versus paclitaxel in patients with relapsed epithelial ovarian cancer showed that these two compounds have similar activity. In this study, a number of patients crossed over to the alternative drug as third-line therapy, ie, from paclitaxel to topotecan and vice versa. We therefore were able to assess the degree of non-cross-resistance between these two compounds.

PATIENTS AND METHODS

Patients who had progressed after one platinum-based regimen were randomized to either topotecan (1.5 mg/m(2)/d) x 5 every 21 days (n = 112) or paclitaxel (175 mg/m(2) over 3 hours) every 21 days (n = 114). A total of 110 patients received cross-over therapy with the alternative drug (61 topotecan, 49 paclitaxel) as third-line therapy.

RESULTS

Response rates to third-line cross-over therapy were 13.1% (8 of 61 topotecan) and 10.2% (5 of 49 paclitaxel; P =.638). Seven patients who responded to third-line topotecan and four patients who responded to paclitaxel had failed to respond to their second-line treatment. Median time to progression (from the start of third-line therapy) was 9 weeks in both groups, and median survival was 40 and 48 weeks for patients who were receiving topotecan or paclitaxel, respectively. The principal toxicity was myelosuppression; grade 4 neutropenia was more frequent with topotecan (81.4% of patients) than with paclitaxel (22.9% of patients).

CONCLUSION

Topotecan and paclitaxel have similar activity as second-line therapies with regard to response rates and progression-free and overall survival. We demonstrated that the two drugs have a degree of non-cross-resistance. Thus, there is a good rationale for incorporating these drugs into future first-line regimens.

Pretreatment with ranitidine does not reduce the bioavailability of orally administered topotecan

PURPOSE

The purpose of this randomized, two-period crossover study was to determine the pharmacokinetics of orally administered topotecan in the presence and absence of oral ranitidine.

METHODS

Patients with solid malignant tumors refractory to standard treatment were given topotecan orally on a daily times five schedule repeated every 21 days. Topotecan was given initially at 2.3 mg/m2 per day; dose adjustments were permitted after the first dose of course 2 if necessary. Blood samples for pharmacokinetic assessments were drawn at protocol-specified times for up to 10 h following oral administration of topotecan on day 1 of courses 1 and 2. Patients were randomly assigned to receive a total of nine doses of ranitidine: 150 mg twice daily for 4 days before day 1 of one of the first two courses and 150 mg given 2 h before the first topotecan dose. Plasma samples were assayed for concentrations of active topotecan lactone (TPT-L) and total topotecan (TPT-T, lactone plus open-ring carboxylate form) using high-performance liquid chromatography with fluorescence detection. After completion of courses 1 and 2, patients could continue on therapy for days 1-5 of every 21 days if not withdrawn due to unacceptable toxicity, disease progression, protocol violation, or by request. Patients continued on treatment for a maximum of six courses.

RESULTS

No pharmacokinetic parameter for either TPT-L or TPT-T differed significantly during administration of topotecan with ranitidine compared with topotecan alone (n = 13). Geometric mean ratios (95% confidence intervals, CIs) of areas under the curve in the presence and absence of ranitidine were 0.94 (0.80, 1.10) for TPT-L and 0.97 (0.80, 1.16) for TPT-T. Corresponding ratios (CIs) of peak plasma concentrations in the presence and absence of ranitidine were 1.06 (0.78, 1.44) for TPT-L and 1.07 (0.84, 1.38) for TPT-T. The median difference in time to peak plasma concentration was 0.0 h for TPT-L and -0.5 h for TPT-T (i.e. slightly faster in the presence of ranitidine).

CONCLUSIONS

Administration of ranitidine prior to oral topotecan resulted in a similar extent of absorption. A slightly faster rate of absorption of topotecan was also observed, which is unlikely to be of clinical significance. Dosage adjustments of orally administered topotecan should not be necessary in patients who are pretreated with ranitidine, an H2 antagonist, or another agent that comparably raises gastric pH.

Stabilization of disease as an indicator of clinical benefit associated with chemotherapy in non-small cell lung cancer patients

In Phase II oncology studies, response rate has traditionally been used to assess activity. However stabilization of disease (SD) may also provide patient benefit. To assess the value of SD (stabilization of measurable disease for at least 8 weeks) as a predictor of survival following chemotherapy in patients with non-small cell lung cancer (NSCLC), we have analyzed data from 198 NSCLC patients receiving topotecan i.v. or orally as first-line therapy either as single agent or in combination. Proportional hazards (Cox) regression models showed that responders [complete response (CR) + partial response (PR), 1.5% and 11.6% respectively] had an estimated risk of death that was 9.8% (95% CI: 4.2% to 22.7%) of that for progressive disease (PD) (60.1% of the patient population). Similarly, patients with SD (26.8% of the patient population) showed a potential benefit with a risk of death that was 27.7% of the one of patients with PD (95% CI: 17.8% to 43.1%). In conclusion SD may be a useful indicator of patient benefit from chemotherapy for NSCLC.

Stabilization of disease as a useful predictor of survival following second-line chemotherapy in small cell lung cancer and ovarian cancer patients

To assess the value of disease stabilization (SD) as a predictor of survival following chemotherapy, data were analyzed from multicenter clinical trials in small cell lung cancer (SCLC) and ovarian cancer (OC) patients receiving various second-line chemotherapy regimens. In both patient populations, SD (lasting >8 weeks) and partial responses (PR) were associated with a survival benefit versus progressive disease (PD); interestingly, the survival benefit was similar between the two groups (PR and SD). These results suggest that, at least in these populations, SD may represent a potential benefit of chemotherapy and therefore the distinction between SD and PR may not be useful.

Topotecan versus cyclophosphamide, doxorubicin, and vincristine for the treatment of recurrent small-cell lung cancer

PURPOSE

Topotecan and cyclophosphamide, doxorubicin, and vincristine (CAV) were evaluated in a randomized, multicenter study of patients with small-cell lung cancer (SCLC) who had relapsed at least 60 days after completion of first-line therapy.

PATIENTS AND METHODS

Patients received either topotecan (1.5 mg/m2) as a 30-minute infusion daily for 5 days every 21 days (n = 107) or CAV (cyclophosphamide 1,000 mg/m2, doxorubicin 45 mg/m2, and vincristine 2 mg) infused on day 1 every 21 days (n = 104). Eligibility included the following: bidimensionally measurable disease, Eastern Cooperative Oncology Group performance status of less than or equal to 2, and adequate marrow, liver, and renal function. Response was confirmed by blinded independent radiologic review.

RESULTS

Response rate was 26 of 107 patients (24.3%) treated with topotecan and 19 of 104 patients (18.3%) treated with CAV (P = .285). Median times to progression were 13.3 weeks (topotecan) and 12.3 weeks (CAV) (P = .552). Median survival was 25.0 weeks for topotecan and 24.7 weeks for CAV (P = .795). The proportion of patients who experienced symptom improvement was greater in the topotecan group than in the CAV group for four of eight symptoms evaluated, including dyspnea, anorexia, hoarseness, and fatigue, as well as interference with daily activity (P< or =.043). Grade 4 neutropenia occurred in 37.8% of topotecan courses versus 51.4% of CAV courses (P<.001). Grade 4 thrombocytopenia and grade 3/4 anemia occurred more frequently with topotecan, occurring in 9.8% and 17.7% of topotecan courses versus 1.4% and 7.2% of CAV courses, respectively (P<.001 for both). Nonhematologic toxicities were generally grade 1 to 2 for both regimens.

CONCLUSION

Topotecan was at least as effective as CAV in the treatment of patients with recurrent SCLC and resulted in improved control of several symptoms.

Topotecan for the treatment of advanced epithelial ovarian cancer: an open-label phase II study in patients treated after prior chemotherapy that contained cisplatin or carboplatin and paclitaxel

PURPOSE

Topotecan, a topoisomerase I inhibitor, was evaluated in a multicenter, phase II study of women with epithelial ovarian carcinoma who relapsed after one or two prior regimens that included platinum and paclitaxel.

PATIENTS AND METHODS

Topotecan 1.5 mg/m2 daily was administered as a 30-minute infusion for 5 consecutive days on a 21-day cycle. Eligibility criteria included bidimensionally measurable disease, Eastern Cooperative Oncology Group performance status of 2 or less, and adequate bone marrow, liver, and renal function. Efficacy was assessed by independent radiologic review.

RESULTS

One hundred thirty-nine patients were treated; 81% were platinum resistant. Sixty-two patients had received one prior regimen and 77 patients had received two prior regimens. Nine patients were not assessable for response; however, all patients were included in the response analysis. The overall response rate was 13.7%; 12.4% in platinum-resistant and 19.2% in platinum-sensitive patients. Stable disease lasted at least 8 weeks in 27.3% of the patients. The median duration of response and time to progression were 18.1 and 12.1 weeks, respectively. The median survival was 47.0 weeks. Grade 4 neutropenia occurred in 82% of the patients (34% of the courses) and thrombocytopenia in 30% of the patients (9% of the courses). Infectious complications occurred in 6% of the courses. Nonhematologic toxicities were mild. There were no drug-related toxic deaths.

CONCLUSION

As a single agent, topotecan has modest activity in women with advanced epithelial ovarian carcinoma who have progressed or not responded after one or two prior regimens with platinum and paclitaxel. Further investigation of combination regimens is indicated in the primary therapy for ovarian cancer based on the mechanism of action and tolerability.

Phase II trial of topotecan as a 21-day continuous infusion in patients with advanced or metastatic adenocarcinoma of the pancreas

The aim of this study was to determine the efficacy and toxicity of topotecan administered as a 21-day continuous intravenous infusion in patients with advanced or metastatic adenocarcinoma of the pancreas. 26 previously untreated patients with advanced or metastatic pancreatic adenocarcinoma received topotecan at a dose of 0.5 mg/m2/day or 0.6 mg/m2/day as a continuous intravenous infusion for 21 days. Courses were repeated every 28 days. 26 patients were assessable for response and toxicity on an intent-to-treat basis. The initial 8 patients at a starting dose of 0.6 mg/m2/day experienced unacceptable myelosuppression and dose delays. The subsequent 18 patients, therefore began therapy at a dose of 0.5 mg/m2/day. The major toxicity of topotecan at this dose and schedule was myelosuppression, which was reversible and non-cumulative. There were no complete responses and two partial responses for a total response rate of 8% (95% confidence interval, 1-25%). Response durations were 17 and 45 weeks. Stable disease was seen in 3 patients. The median time to progression for all patients was 8 weeks and the median survival was 20 weeks. Topotecan given as a 21-day continuous intravenous infusion has a similar response rate and median survival to our previously reported study of the 5-day short infusion regimen in pancreatic carcinoma.

Phase I study of high-dose etoposide phosphate in man

Etoposide is a widely used cytotoxic agent with a broad spectrum of activity in human malignancies. This agent has been incorporated into many transplant regimens although toxicity occurs because of its poor water solubility and toxic excipients. Etoposide phosphate, a water soluble prodrug of etoposide, has been studied at conventional dosages in man and shown to have advantages over the parent compound. We have extended our previous experience with this new agent to evaluate the levels needed in transplantation protocols. This phase I study of intravenous high-dose etoposide phosphate over 2 h on days 1 and 2 was designed to determine whether or not dose linearity between the amount of etoposide phosphate administered to patients and generation of etoposide in vivo as seen with conventional dosages of this agent would be present at transplant-dose levels. In addition, the toxicities of these dose levels with the short infusion schedule were defined. A conservative dose escalation scheme was chosen based upon prior knowledge of etoposide. Thirty-one patients (19 male, 12 female) with CALGB performance status 0-1 with a variety of solid tumors entered this study. The patients were treated with dose levels of etoposide phosphate given as the etoposide-equivalent doses of 250, 500, 750, 1000, 1200, 1400, and 1600 mg/m2/day in 250-400 ml of normal saline given as an intravenous infusion over 2 h on days 1 and 2 every 28 days. After the maximal tolerated dose level was determined on this schedule, additional patients received etoposide phosphate as a 4 h infusion on both days in an attempt to reduce toxicities. G-CSF (5 micrograms/kg/day) was administered subcutaneously to all patients from day 3 until the WBC > or = 10000/microliters. Nonhematologic toxicity was considered to be dose limiting. Serial plasma samples for pharmacokinetics were obtained from patients on day 1 of cycle 1. For the 2 h infusion, the maximum tolerated dose of etoposide phosphate was 1000 mg/m2/day x 2 with dose limiting mucositis. In the small number of patients studied, the maximum tolerated dose was reached for the 4 h infusion at 1400 mg/m2/day of drug, again due to mucositis. Other toxicities, despite the rapid infusion schedule, were modest with transient mild headache being most common. At the highest doses etoposide phosphate was efficiently and rapidly dephosphorylated to etoposide. Etoposide generated by dephosphorylation of etoposide phosphate had plasma disposition curves characteristic of etoposide administered parenterally. One partial response occurred in a patient with small cell lung cancer. Etoposide phosphate can be rapidly infused in modest fluid volumes at dosages required for transplantation protocols with minimal acute side-effects. On a 2 h schedule, mucositis becomes the dose limiting nonhematologic toxicity. Mucositis seems to correlate with peak dose levels of the drug rather than total drug administered. On a 4 h infusion schedule given sequentially for 2 days, the maximum tolerated dosage could be increased 40% compared to the 2 h schedule. The relative ease of administration and the rapid conversion of this prodrug into etoposide should make it useful in high-dose therapy settings.

Pharmacokinetic evaluation of high-dose etoposide phosphate after a 2-hour infusion in patients with solid tumors

Etoposide phosphate, a water soluble prodrug of etoposide, was evaluated at levels potentially useful in transplantation settings in patients with malignancies. For pharmacokinetic studies of etoposide phosphate in this phase I study, 21 patients with solid tumors were treated with etoposide phosphate given as etoposide equivalents of 250, 500, 750, 1000 and 1200 mg/m2 infused over 2 h on days 1 and 2, and G-CSF 5 micrograms/kg per day starting on day 3 until WBC was > or = 10,000/microliters. Qualitative, quantitative, and pharmacokinetic analysis was performed as reported previously. Rapid conversion of etoposide phosphate into etoposide by dephosphorylation occurred at all dosage levels without indication of saturation of phosphatases. Plasma levels (C(pmax)) and area under the curve (AUC) of etoposide phosphate and etoposide demonstrated linear dose effects. For etoposide, plasma disposition demonstrated biphasic clearance, with mean T1/2 alpha of 2.09 +/- 0.61 h, and T1/2 beta of 5.83 +/- 1.71 h. An AUC as high as 1768.50 micrograms.h/ml was observed at a dose of 1200 mg/m2. The total body clearance (TBC) showed an overall mean of 15.72 +/- 4.25 ml/min per m2, and mean volume of distribution (VDss) of 5.64 +/- 1.06 l/m2. The mean residual time (MRT) for etoposide was 6.24 +/- 1.61 h. In urine, etoposide but not etoposide phosphate, was identified with large quantitative variations (1.83% to 33.45% of injected etoposide equivalents). These results indicate that etoposide phosphate is converted into etoposide with the linear dose-related C(pmax) and AUCs necessary for use of this agent at the high dosage levels needed in transplantation protocols. A comparison of pharmacokinetic parameters of high-dose etoposide with the values observed in our study with etoposide phosphate revealed comparable values for the clinically important C(pmax) and AUCs, clearance, terminal T1/2 and MRT. In contrast to the use of etoposide, etoposide phosphate can be delivered in aqueous vehicles and therefore may offer the advantage of ease of administration.

Pharmacokinetics and bioequivalence of etoposide following intravenous administration of etoposide phosphate and etoposide in patients with solid tumors

PURPOSE

To assess the pharmacokinetics and bioequivalence of etoposide following intravenous (i.v.) administration of etoposide phosphate (Etopophos; Bristol-Myers Squibb, Princeton, NJ), a prodrug of etoposide, and VePesid (Bristol-Myers Squibb).

PATIENTS AND METHODS

Forty-nine solid tumor patients were randomized to receive Etopophos or VePesid on day 1 of a day-1,3,5 schedule of treatment. The alternate drug was given on day 3 and repeated on day 5. The dose, 150 mg/m2 of etoposide equivalent, was administered by constant rate infusion over 3.5 hours. The plasma concentrations of etoposide phosphate and etoposide were determined using validated high-performance liquid chromatography (HPLC) assays. Pharmacokinetic parameters were calculated by a noncompartmental method. Etopophos was considered to be bioequivalent to VePesid if the 90% confidence limits for the differences in mean maximum concentration (Cmax) and AUCinf of etoposide were contained within 80% to 125% for the long-transformed data.

RESULTS

Forty-one patients were assessable for pharmacokinetics and bioequivalence assessment. Following i.v. administration, etoposide phosphate was rapidly and extensively converted to etoposide in systemic circulation, resulting in insufficient data to estimate its pharmacokinetics. The mean bioavailability of etoposide from Etopophos, relative to VePesid, was 103% (90% confidence interval, 99% to 106%) based on Cmax, and 107% (90 confidence interval, 105% to 110%) based on area under the concentration versus time curve from zero to infinity (AUCinf) values. Mean terminal elimination half-life (t1/2), steady-state volume of distribution (Vss), and total systemic clearance (CL) values of etoposide were approximately 7 hours, 7 L/m2, and 17 mL/min/m2 after Etopophos and VePesid treatments, respectively. The main toxicity observed was myelosuppression, characterized by leukopenia and neutropenia.

CONCLUSION

With respect to plasma levels of etoposide, i.v. Etopophos is bioequivalent to i.v. VePesid.

Phase I study of etoposide phosphate (etopophos) as a 30-minute infusion on days 1, 3, and 5

Etoposide phophate is a phosphate ester prodrug of etoposide designed to improve the pharmaceutical characteristics of the parent compound. A Phase I dose-escalating study of etoposide phosphate was conducted concurrently at two institutions to determine its toxicity, pharmacokinetics, and maximum tolerated dose. Etoposide phosphate was administered i.v. for 30 min on days 1, 3, and 5 every 21 days or on recovery from toxicity. Cohorts of at least three patients received etoposide phosphate at dose levels from 50 mg/m2 to 150 mg/m2 expressed as molar equivalents of etoposide. Blood and urine samples were obtained from all patients during the first cycle of treatment and the concentrations of etoposide phosphate and etoposide were measured. Thirty-nine patients with documented cancers received a total of 75 cycles of etoposide phosphate. The dose-limiting toxicity was myelosuppression which occurred at the 150-mg/m2 etoposide equivalent dose. Etoposide phosphate was rapidly and extensively converted to etoposide. No measurable etoposide phosphate was detectable in the plasma by 15-60 min after the end of the infusion. The mean half-life of etoposide at the different dose levels ranged from 5.5 to 9.3 h. The pharmacokinetics of etoposide, generated from etoposide phosphate, was linear over the dose range studied and was comparable to results reported in the literature for i.v. etoposide. In summary, i.v. etoposide phosphate is rapidly and extensively converted to etoposide. The maximum tolerated dose of etoposide phosphate when given on days 1, 3, and 5 is 150 mg/m2/day. The dose-limiting toxicity is myelosuppression. The maximum tolerated dose and adverse event profile are consistent with those of etoposide.

Phase I study of topotecan and cisplatin in patients with advanced solid tumors: a cancer and leukemia group B study

PURPOSE

The objectives of this phase I trial were to determine the dose-limiting toxicities (DLTs) of the novel topoisomerase I inhibitor topotecan combined with cisplatin, to define the maximum-tolerated doses (MTDs) of the combination without and with the use of filgrastim, and to define recommended doses for phase II trials.

PATIENTS AND METHODS

Patients with advanced solid tumors were eligible if they had normal bone marrow, renal, and hepatic function and had not previously been treated with platinum compounds. Topotecan was administered intravenously on days 1 through 5 and cisplatin was administered intravenously on day 1 of a 21-day cycle. The topotecan dose was fixed at 1.0 mg/m2/d on the first four dose levels, and cisplatin was escalated in 25-mg/m2 increments from 25 to 100 mg/m2 without filgrastim. After encountering DLT, the dose of cisplatin was decreased by one level and topotecan dose escalation was attempted. After defining the MTD without growth factor, the study proceeded with escalating cisplatin doses to define the MTD with filgrastim 5 micrograms/kg subcutaneously (SC) daily starting on day 6 of treatment. Priming with filgrastim 5 micrograms/kg SC on days -6 to -2 before the first course was explored last.

RESULTS

Of 38 patients entered, 37 were eligible, 35 assessable for toxicity in the first course, and 28 assessable for response. The principal toxicity was grade 4 neutropenia, which had to last more than 7 days to be considered dose-limiting. No DLT was observed at the starting cisplatin dose of 25 mg/m2 (dose level 1). On level 2 (cisplatin 50 mg/m2, one patient had dose-limiting neutropenia and one patient had grade 3 renal toxicity. On level 3 (cisplatin 75 mg/m2), two patients had dose-limiting neutropenia. Therefore, cisplatin dose escalation was stopped. On dose level 5 (cisplatin 50 mg/m2 and topotecan 1.25 mg/m2/d), one patient had grade 4 neutropenia that lasted more than 7 days and one patient died of neutropenic sepsis. The remaining dose levels used topotecan 1.0 mg/m2/d plus cisplatin 75 mg/m2 (level 6) and 100 mg/m2 (levels 7 and 8) with filgrastim. No DLT was observed on level 6. On level 7, two patients had dose-limiting neutropenia and one patient had grade 3 hyperbilirubinemia. Priming with filgrastim on level 8 demonstrated no obvious advantage over level 7, and one patient had grade 4 thrombocytopenia that lasted more than 7 days. Three patients with non-small-cell lung cancer achieved a partial response and one patient with breast cancer had a complete response.

CONCLUSION

Topotecan and cisplatin in combination cause more neutropenia than expected from either drug given alone at the same dosage. The recommended phase II doses are topotecan 1.0 mg/m2/d for 5 days in combination with cisplatin 50 mg/m2 on day 1 without filgrastim or cisplatin 75 mg/m2 on day 1 with filgrastim support.

Subcellular distribution of daunorubicin in P-glycoprotein-positive and -negative drug-resistant cell lines using laser-assisted confocal microscopy

Four well defined multidrug-resistant cell lines and their drug-sensitive counterparts were examined for intracellular distribution of daunorubicin (DNR) by laser-assisted confocal fluorescence microscopy: P-glycoprotein-negative HL-60/AR cells, and P-glycoprotein-positive P388/ADR, KBV-1, and MCF-7/ADR cells. Both drug sensitive cell lines (HL-60/S, P388/S, KB3-1, and MCF-7/S) and drug-resistant cell lines (HL-60/AR, P388/ADR, KBV-1, and MCF-7/ADR) exposed to DNR showed a similar rapid distribution of drug from the plasma membrane to the perinuclear region within the first 2 min. From 2-10 min, the drug sensitive HL-60/S, P388/S, and MCF-7/S cells redistributed drug to the nucleus and to the cytoplasm in a diffuse pattern. In contrast, drug-resistant HL-60/AR, P388/ADR, and MCF-7/ADR redistributed DNR from the perinuclear region into vesicles distinct from nuclear structures, thereby assuming a "punctate" pattern. This latter redistribution could be inhibited by glucose deprivation (indicating energy dependence), or by lowering the temperature of the medium below 18 degrees C. The differences in distribution between sensitive and resistant cells did not appear to be a function of intracellular DNR content, nor the result of drug cytotoxicity. Drug-sensitive KB3-1 and -resistant KBV-1 cells did not fully follow this pattern in that they demonstrated an intracellular DNR distribution intermediate between HL-60/S and HL-60/AR cells with both "punctate" and nuclear/cytoplasmic uptake sometimes in the same cell. These data indicate that the intracellular distribution of DNR is an important determinant of drug resistance regardless of the overexpression of P-glycoprotein. The intracellular movement of drug requires the presence of glucose and a temperature above 18 degrees C, implicating energy-dependent processes and vesicle fusion in the distribution process. This intracellular transport of DNR away from the nucleus in multidrug-resistant cells may protect putative cell targets such as DNA against drug toxicity.