The concept of exploiting the specific binding properties of monoclonal antibodies as a mechanism for selective delivery of cytotoxic agents to tumor cells is an attractive solution to the challenge ...of increasing the therapeutic index of cell-killing agents for treating cancer. All three parts of an antibody-drug conjugate (ADC)-the antibody, the cytotoxic payload, and the linker chemistry that joins them together-as well as the biologic properties of the cell-surface target antigen are important in designing an effective anticancer agent. The approval of brentuximab vedotin in 2011 for treating relapsed Hodgkin's lymphoma and systemic anaplastic large cell lymphoma, and the approval of ado-trastuzumab emtansine in 2013 for treating HER2-positive metastatic breast cancer, have sparked vigorous research in the field, with >65 ADCs currently in clinical evaluation. This review highlights the ADCs that are approved for marketing, in pivotal clinical trials, or in at least phase II clinical development for treating both hematologic malignancies and solid tumors.
Tivozanib is a potent and selective tyrosine kinase inhibitor of vascular endothelial growth factor receptor 1 (VEGFR1), -2, and -3. This phase III trial compared tivozanib with sorafenib as initial ...targeted therapy in patients with metastatic renal cell carcinoma (RCC).
Patients with metastatic RCC, with a clear cell component, prior nephrectomy, measurable disease, and 0 or 1 prior therapies for metastatic RCC were randomly assigned to tivozanib or sorafenib. Prior VEGF-targeted therapy and mammalian target of rapamycin inhibitor were not permitted. The primary end point was progression-free survival (PFS) by independent review.
A total of 517 patients were randomly assigned to tivozanib (n = 260) or sorafenib (n = 257). PFS was longer with tivozanib than with sorafenib in the overall population (median, 11.9 v 9.1 months; hazard ratio HR, 0.797; 95% CI, 0.639 to 0.993; P = .042). One hundred fifty-six patients (61%) who progressed on sorafenib crossed over to receive tivozanib. The final overall survival (OS) analysis showed a trend toward longer survival on the sorafenib arm than on the tivozanib arm (median, 29.3 v 28.8 months; HR, 1.245; 95% CI, 0.954 to 1.624; P = .105). Adverse events (AEs) more common with tivozanib than with sorafenib were hypertension (44% v 34%) and dysphonia (21% v 5%). AEs more common with sorafenib than with tivozanib were hand-foot skin reaction (54% v 14%) and diarrhea (33% v 23%).
Tivozanib demonstrated improved PFS, but not OS, and a differentiated safety profile, compared with sorafenib, as initial targeted therapy for metastatic RCC.
Temsirolimus, a specific inhibitor of the mammalian target of rapamycin kinase, has shown clinical activity in mantle cell lymphoma (MCL). We evaluated two dose regimens of temsirolimus in comparison ...with investigator's choice single-agent therapy in relapsed or refractory disease.
In this multicenter, open-label, phase III study, 162 patients with relapsed or refractory MCL were randomly assigned (1:1:1) to receive one of two temsirolimus regimens: 175 mg weekly for 3 weeks followed by either 75 mg (175/75-mg) or 25 mg (175/25-mg) weekly, or investigator's choice therapy from prospectively approved options. The primary end point was progression-free survival (PFS) by independent assessment.
Median PFS was 4.8, 3.4, and 1.9 months for the temsirolimus 175/75-mg, 175/25-mg, and investigator's choice groups, respectively. Patients treated with temsirolimus 175/75-mg had significantly longer PFS than those treated with investigator's choice therapy (P = .0009; hazard ratio = 0.44); those treated with temsirolimus 175/25-mg showed a trend toward longer PFS (P = .0618; hazard ratio = 0.65). Objective response rate was significantly higher in the 175/75-mg group (22%) compared with the investigator's choice group (2%; P = .0019). Median overall survival for the temsirolimus 175/75-mg group and the investigator's choice group was 12.8 months and 9.7 months, respectively (P = .3519). The most frequent grade 3 or 4 adverse events in the temsirolimus groups were thrombocytopenia, anemia, neutropenia, and asthenia.
Temsirolimus 175 mg weekly for 3 weeks followed by 75 mg weekly significantly improved PFS and objective response rate compared with investigator's choice therapy in patients with relapsed or refractory MCL.
Recent data showed improvement in progression-free survival (PFS) when adding everolimus to exemestane in patients with advanced breast cancer experiencing recurrence/progression after nonsteroidal ...aromatase inhibitor (AI) therapy. Here, we report clinical outcomes of combining the mammalian target of rapamycin (mTOR) inhibitor temsirolimus with letrozole in AI-naive patients.
This phase III randomized placebo-controlled study tested efficacy/safety of first-line oral letrozole 2.5 mg daily/temsirolimus 30 mg daily (5 days every 2 weeks) versus letrozole/placebo in 1,112 patients with AI-naive, hormone receptor-positive advanced disease. An independent data monitoring committee recommended study termination for futility at the second preplanned interim analysis (382 PFS events).
Patients were balanced (median age, 63 years; 10% stage III, 40% had received adjuvant endocrine therapy). Those on letrozole/temsirolimus experienced more grade 3 to 4 events (37% v 24%). There was no overall improvement in primary end point PFS (median, 9 months; hazard ratio HR, 0.90; 95% CI, 0.76 to 1.07; P = .25) nor in the 40% patient subset with prior adjuvant endocrine therapy. An exploratory analysis showed improved PFS favoring letrozole/temsirolimus in patients ≤ age 65 years (9.0 v 5.6 months; HR, 0.75; 95% CI, 0.60 to 0.93; P = .009), which was separately examined by an exploratory analysis of 5-month PFS using subpopulation treatment effect pattern plot methodology (P = .003).
Adding temsirolimus to letrozole did not improve PFS as first-line therapy in patients with AI-naive advanced breast cancer. Exploratory analyses of benefit in younger postmenopausal patients require external confirmation.
Human epidermal growth factor (HER) -mediated signaling is critical in many cancers, including subsets of breast and lung cancer. HER family members signal via the phosphatidylinositide 3-kinase ...(PI3K) -AKT/protein kinase B-mammalian target of rapamycin (mTOR) cascade; mTOR activation is critical for the expression of multiple contributors to tumor growth and invasion. On the basis of preclinical data suggesting synergy of HER2 inhibition and mTOR inhibition in breast and lung cancer models, we conducted a phase I combination study of neratinib, a small-molecule irreversible pan-HER tyrosine kinase inhibitor, and temsirolimus, an mTOR inhibitor, in patients with advanced solid tumors.
This study enrolled patients to dosing combinations of neratinib and temsirolimus. The primary objective was to estimate the toxicity contour of the combination and establish recommended phase II doses.
Sixty patients were treated on 12 of 16 possible dosing combinations. Diarrhea was the most common drug-related (93%) and dose-limiting toxicity (DLT), constituting four of 10 DLTs. Dose-limiting grade 3 metabolic abnormalities were also observed. Other frequent drug-related toxicities included nausea, stomatitis (both 53%), and anemia (48%). Two maximum-tolerated dose combinations were identified: 200 mg of neratinib/25 mg of temsirolimus and 160 mg of neratinib/50 mg of temsirolimus. Responses were noted in patients with HER2-amplified breast cancer resistant to trastuzumab, HER2-mutant non-small-cell lung cancer, and tumor types without identified mutations in the HER-PI3K-mTOR pathway.
The combination of neratinib and temsirolimus was tolerable and demonstrated antitumor activity in multiple tumor types, warranting further evaluation.
Angiogenesis is important for epithelial ovarian cancer (EOC) growth, and blocking angiogenesis can lead to EOC regression. Cediranib is an oral tyrosine kinase inhibitor (TKI) of vascular ...endothelial growth factor receptor (VEGFR) -1, VEGFR-2, VEGFR-3, and c-kit.
We conducted a phase II study of cediranib for recurrent EOC or peritoneal or fallopian tube cancer; cediranib was administered as a daily oral dose, and the original dose was 45 mg daily. Because of toxicities observed in the first 11 patients, the dose was lowered to 30 mg. Eligibility included <or= two lines of chemotherapy for recurrence. End points included response rate (via Response Evaluation Criteria in Solid Tumors RECIST or modified Gynecological Cancer Intergroup CA-125), toxicity, progression-free survival (PFS), and overall survival (OS).
Forty-seven patients were enrolled; 46 were treated. Clinical benefit rate (defined as complete response CR or partial response PR, stable disease SD > 16 weeks, or CA-125 nonprogression > 16 weeks), which was the primary end point, was 30%; eight patients (17%; 95% CI, 7.6% to 30.8%) had a PR, six patients (13%; 95% CI, 4.8% to 25.7%) had SD, and there were no CRs. Eleven patients (23%) were removed from study because of toxicities before two cycles. Grade 3 toxicities (> 20% of patients) included hypertension (46%), fatigue (24%), and diarrhea (13%). Grade 2 hypothyroidism occurred in 43% of patients. Grade 4 toxicities included CNS hemorrhage (n = 1), hypertriglyceridemia/hypercholesterolemia/elevated lipase (n = 1), and dehydration/elevated creatinine (n = 1). No bowel perforations or fistulas occurred. Median PFS was 5.2 months, and median OS has not been reached; median follow-up time is 10.7 months.
Cediranib has activity in recurrent EOC, tubal cancer, and peritoneal cancer with predictable toxicities observed with other TKIs.
Pneumonitis has occurred in patients treated with inhibitors of the mammalian target of rapamycin (mTOR). In a phase III study of patients with previously untreated, poor-prognosis, advanced renal ...cell carcinoma (ARCC), the mTOR inhibitor temsirolimus improved survival compared with interferon. We performed a retrospective, independent, blinded radiographic review of chest computed tomography (CT) images of patients in this study to characterize temsirolimus-related pneumonitis.
Patients were treated with intravenous temsirolimus 25 mg once weekly or subcutaneous interferon alfa 3 million units, with an increase to 18 million units, thrice weekly. Drug-related pneumonitis was identified based on sequential chest CT images, required every 8 weeks, showing changes consistent with pneumonitis and not pneumonia (infection) or disease progression as correlated with clinical data. Cumulative probability of drug-related pneumonitis was estimated using the Kaplan-Meier method.
Eight (6%) of 138 and 52 (29%) of 178 evaluable patients on interferon and temsirolimus treatment, respectively, developed radiographically identified drug-related pneumonitis. Time to onset of pneumonitis was significantly shorter on the temsirolimus arm than on the interferon arm (log-rank P < .001). Estimated cumulative probability of pneumonitis at 8 and 16 weeks from first dose was 21% and 31%, respectively, on the temsirolimus arm and 6% and 8%, respectively, on the interferon arm. Respiratory symptoms were observed around time of onset of radiographically diagnosed temsirolimus-related pneumonitis in 16 (31%) of 52 patients.
Patients with ARCC receiving temsirolimus should be monitored closely for development of pneumonitis, and their management should be altered if clinical symptoms appear.
To determine dose-limiting toxicities, maximum-tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of weekly intravenous temsirolimus, a mammalian target of rapamycin (mTOR) signaling ...pathway inhibitor, in pediatric patients with recurrent or refractory solid tumors.
Cohorts of three to six patients 1 to 21 years of age with recurrent or refractory solid tumors were treated with a 1-hour intravenous infusion of temsirolimus weekly for 3 weeks per course at one of four dose levels: 10, 25, 75, or 150 mg/m(2). During the first two courses, pharmacokinetic and pharmacodynamic evaluations (phosphorylation of S6, AKT, and 4EBP1 in peripheral-blood mononuclear cells) were performed.
Dose-limiting toxicity (grade 3 anorexia) occurred in one of 18 evaluable patients at the 150 mg/m(2) level, which was determined to be tolerable, and an MTD was not identified. In 13 patients evaluable for response after two courses of therapy, one had complete response (CR; neuroblastoma) and five had stable disease (SD). Four patients (three SDs + one CR) remained on treatment for more than 4 months. The sum of temsirolimus and sirolimus areas under the concentration-time curve was comparable to values in adults. AKT and 4EBP1 phosphorylation were inhibited at all dose levels, particularly after two courses.
Weekly intravenous temsirolimus is well tolerated in children with recurrent solid tumors, demonstrates antitumor activity, has pharmacokinetics similar to those in adults, and inhibits the mTOR signaling pathway in peripheral-blood mononuclear cells. Further studies are needed to define the optimal dose for use in combination with other antineoplastic agents in pediatric patients.
Learning Objectives
After completing this course, the reader will be able to:
Discuss the role of chemotherapy in the treatment of brain metastases.
Identify the properties of topotecan that are ...conducive to treating patients with brain metastases.
Discuss the investigation of single‐agent topotecan and topotecan in combination with other chemotherapeutic agents or radiotherapy in the treatment of brain metastases.
Access and take the CME test online and receive one hour of AMA PRA category 1 credit at CME.TheOncologist.com
Despite advances in the treatment of systemic malignancies, the prognosis for patients with brain metastases continues to be dismal. Because the majority of cytotoxic agents seem to be unable to penetrate the blood‐brain barrier, the role of chemotherapy in the treatment of brain metastases remains controversial. However, growing amounts of both laboratory and clinical data suggest that a few of the newly developed cytotoxic agents can cross the blood‐brain barrier and may have a role in the treatment of patients with brain metastases. Topotecan, a novel topoisomerase I inhibitor, freely crosses the blood‐brain barrier and may be clinically effective in both the therapeutic and prophylactic settings in patients with brain metastases. Recent studies have demonstrated the antitumor activity of topotecan against brain metastases, with objective response rates ranging from 33%‐63% in patients with various solid tumors. The antitumor response in the central nervous system was often greater and occurred more quickly than the systemic antitumor response to topotecan treatment. This result may be explained by the lack of exposure of brain metastases to previous cytotoxic agents, suggesting a role for topotecan in patients with brain metastases. Early studies have also suggested that topotecan, an apparent radiosensitizer, may be particularly effective in combination with radiotherapy, the current standard of care for patients with brain metastases. In addition, preliminary data suggest that topotecan in combination with temozolomide (another cytotoxic agent that can cross the blood‐brain barrier) may have synergistic antitumor activity against brain metastases. This review summarizes the available preclinical and clinical evidence for the role of topotecan in the treatment of brain metastases and concludes with three case studies.
STA-4783 is a new compound that markedly enhances the therapeutic index of paclitaxel against human tumor xenograft models. A phase I clinical trial was undertaken to determine the maximum tolerated ...dose, toxicity profile, and pharmacokinetics of STA-4783 in combination with paclitaxel.
Adults with refractory solid tumors concurrently received STA-4783 and paclitaxel as a 3-h i.v. infusion at starting doses of 44 and 135 mg/m(2), respectively. After increasing paclitaxel to 175 mg/m(2), the STA-4783 dose was escalated as permitted by dose-limiting toxicity during the first 21-day cycle.
Thirty-five patients were treated with eight dose levels of STA-4783/paclitaxel. In patients receiving 175 mg/m(2) paclitaxel, the incidence of severe toxicity increased with escalation of the STA-4783 dose above 263 mg/m(2), and 438 mg/m(2) was the maximum tolerated dose. All toxicities were typical of paclitaxel, with neutropenia, mucositis, and myalgia/arthralgia being dose limiting. Partial responses were achieved in one patient with Kaposi's sarcoma and another with ovarian cancer that progressed during prior treatment with paclitaxel. STA-4783 exhibited linear pharmacokinetics characterized by rapid elimination from plasma (biological half-life, 1.06 +/- 0.24 h) and a low steady-state apparent volume of distribution (25.1 +/- 8.1 L/m(2)). The total body clearance of paclitaxel decreased significantly with escalation of the STA-4783 dose.
The STA-4783/paclitaxel combination was well tolerated with a toxicity profile similar to single-agent paclitaxel. Enhanced systemic exposure to paclitaxel resulting from a dose-dependent interaction with STA-4783 was associated with increased toxicity. Objective responses in two heavily pretreated patients, both with taxane exposure, have encouraged further clinical evaluation of this regimen.
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