Background
Most targeted anticancer therapies, as well as cytotoxic and radiation therapies, are encumbered by the development of secondary resistance by cancer cells. Resistance is a complex ...phenomenon involving multiple mechanisms, including activation of signaling pathways such as phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR). Novel strategies to overcome resistance by targeting these signaling pathways are being evaluated.
Methods
PubMed and key cancer congress abstracts were searched until July 2012 for preclinical and clinical data relating to the PI3K/AKT/mTOR pathway and anticancer treatment resistance, and use of PI3K/AKT/mTOR inhibitors in resistant cancer cell lines and patient populations.
Results
Activation of the PI3K/AKT/mTOR pathway is frequently implicated in resistance to anticancer therapies, including biologics, tyrosine kinase inhibitors, radiation, and cytotoxics. As such, inhibitors of the PI3K/AKT/mTOR pathway are being rapidly evaluated in preclinical models and in clinical studies to determine whether they can restore therapeutic sensitivity when given in combination. In breast cancer, non-small-cell lung cancer, and glioblastoma, we find compelling preclinical evidence to show that inhibitors of PI3K or mTOR can restore sensitivity in resistant cells. Although clinical evidence is less mature, a recent Phase III study with the mTORC1 inhibitor everolimus in patients with advanced breast cancer resistant to aromatase inhibition and several Phase I/II studies with PI3K inhibitors demonstrate proof-of-concept, warranting future clinical evaluation.
Conclusion
Current preclinical and clinical evidence suggest that inhibitors of the PI3K/AKT/mTOR pathway could have utility in combination with other anticancer therapies to circumvent resistance by cancer cells. Multiple clinical studies are ongoing.
The landscape of cancer therapy has been transformed by advances in clinical next‐generation sequencing, genomically targeted therapies, and immunotherapies. Well designed clinical trials and ...efficient clinical trial conduct are crucial for advancing our understanding of cancer, improving patient outcomes, and identifying personalized treatments. Basket trials have emerged as one of the efficient modern clinical trial designs that evaluate the efficacy of these therapies across multiple cancer types based on specific molecular alterations or biomarkers, irrespective of histology or anatomic location. This review delves into the evolution of basket trials in cancer drug development, highlighting their potential prospects and current obstacles. The design of basket trials involves screening patients for specific molecular alterations or biomarkers and enrolling them in the trial to receive the targeted therapy under investigation. Statistical considerations play a crucial role in the design, analysis, and interpretation of basket trials. Several notable examples of basket trials that have led to US Food and Drug Administration approval for uncommon molecular alterations (e.g., NTRK fusions, BRAF mutations, RET and FGFR1 alterations) are discussed, including LOXO‐TRK (ClinicalTrials.gov identifier NCT02122913)/SCOUT (ClinicalTrials.gov identifier NCT02637687)/NAVIGATE (ClinicalTrials.gov identifier NCT02576431)/STARTRK (ClinicalTrials.gov identifiers NT02097810, NT02568267), VE‐BASKET (ClinicalTrials.gov identifier NCT01524978), ROAR Basket (ClinicalTrials.gov identifier NCT02034110), LIBRETTO‐001 (ClinicalTrials.gov identifier NCT03157128), ARROW (ClinicalTrials.gov identifier NCT03037385), FIGHT‐203 (ClinicalTrials.gov identifier NCT03011372), and the National Cancer Institute‐Molecular Analysis for Therapy Choice trial (ClinicalTrials.gov identifier NCT02465060). Basket trials have the potential to revolutionize cancer treatment by identifying effective therapies for patients based on specific molecular alterations or biomarkers rather than traditional histology‐based approaches.
Plain Language Summary
To gain more knowledge about cancer, improve patient outcomes, and discover personalized treatments, it is crucial to conduct clinical trials efficiently.
One effective type of clinical trial is called a basket trial.
In basket trials, new treatments are tested on various types of cancer, regardless of their location in the body; instead, researchers focus on specific abnormalities in the cancer cells.
Basket trials offer hope that we can find personalized treatments that are more effective for each individual battling cancer.
Advances in next‐generation sequencing, targeted therapies, and immunotherapies have transformed cancer therapy. Efficient basket trials evaluate the effectiveness of these therapies across different types of cancer based on specific molecular alterations, offering potential for personalized treatments and revolutionizing cancer care.
The antibody-drug conjugate trastuzumab-DM1 (T-DM1) combines the biologic activity of trastuzumab with targeted delivery of a potent antimicrotubule agent, DM1, to human epidermal growth factor ...receptor 2 (HER2)-overexpressing cancer cells. Based on results from a phase I study that showed T-DM1 was well tolerated at the maximum-tolerated dose of 3.6 mg/kg every 3 weeks, with evidence of efficacy, in patients with HER2-positive metastatic breast cancer (MBC) who were previously treated with trastuzumab, we conducted a phase II study to further define the safety and efficacy of T-DM1 in this patient population.
This report describes a single-arm phase II study (TDM4258g) that assessed efficacy and safety of intravenous T-DM1 (3.6 mg/kg every 3 weeks) in patients with HER2-positive MBC who had tumor progression after prior treatment with HER2-directed therapy and who had received prior chemotherapy.
With a follow-up of ≥ 12 months among 112 treated patients, the objective response rate by independent assessment was 25.9% (95% CI, 18.4% to 34.4%). Median duration of response was not reached as a result of insufficient events (lower limit of 95% CI, 6.2 months), and median progression-free survival time was 4.6 months (95% CI, 3.9 to 8.6 months). The response rates were higher among patients with confirmed HER2-positive tumors (immunohistochemistry 3+ or fluorescent in situ hybridization positive) by retrospective central testing (n = 74). Higher response rates were also observed in patients whose tumors expressed ≥ median HER2 levels by quantitative reverse transcriptase polymerase chain reaction for HER2 expression, compared with patients who had less than median HER2 levels. T-DM1 was well tolerated with no dose-limiting cardiotoxicity. Most adverse events (AEs) were grade 1 or 2; the most frequent grade ≥ 3 AEs were hypokalemia (8.9%), thrombocytopenia (8.0%), and fatigue (4.5%).
T-DM1 has robust single-agent activity in patients with heavily pretreated, HER2-positive MBC and is well tolerated at the recommended phase II dose.
Amplified PI3K/Akt/mTOR signaling is common in metastatic breast cancer (MBC). The mTOR inhibitor everolimus improves progression-free survival (PFS) when added to steroidal aromatase inhibitor ...therapy. This randomized phase II trial compares the efficacy of paclitaxel/bevacizumab/everolimus and paclitaxel/bevacizumab/placebo as first-line treatment for MBC. Patients with untreated HER2-negative MBC were randomized (1:1) to receive 28-day cycles of paclitaxel 90 mg/m
2
IV (days 1, 8, and 15) and bevacizumab 10 mg/kg IV (days 1, 15) with either everolimus 10 mg (Arm 1) or placebo (Arm 2) daily. Treatment continued (evaluation every 8 weeks) until progression or unacceptable toxicity. Treatment of 110 patients allowed detection of an improvement in median PFS from 11 to 16 months (70 % power,
α
= 0.10). Between August 2009 and June 2011, 113 patients (median age 58 years; 88 % ER or PR positive) were randomized (Arm 1, 56; Arm 2, 57). Patients in both arms received a median of six treatment cycles. Median PFS (95 % CI) was 9.1 months (6.8–18.8) for Arm 1, and 7.1 months (5.6–10.8) for Arm 2 (
p
= 0.89). Comparisons of other efficacy endpoints were also similar in the two treatment arms. Patients receiving everolimus had more anemia, stomatitis, diarrhea, rash, and arthralgia/myalgia, although the overall incidence of severe (grade 3/4) toxicity was similar. The addition of everolimus did not improve the efficacy of weekly paclitaxel/bevacizumab as first-line treatment for patients with HER2-negative MBC. These results contrast with the demonstrated efficacy of adding everolimus to either hormonal or HER2-targeted therapy in previously treated patients.
Resistance to therapy with BRAF kinase inhibitors is associated with reactivation of the mitogen-activated protein kinase (MAPK) pathway. To address this problem, we conducted a phase 1 and 2 trial ...of combined treatment with dabrafenib, a selective BRAF inhibitor, and trametinib, a selective MAPK kinase (MEK) inhibitor.
In this open-label study involving 247 patients with metastatic melanoma and BRAF V600 mutations, we evaluated the pharmacokinetic activity and safety of oral dabrafenib (75 or 150 mg twice daily) and trametinib (1, 1.5, or 2 mg daily) in 85 patients and then randomly assigned 162 patients to receive combination therapy with dabrafenib (150 mg) plus trametinib (1 or 2 mg) or dabrafenib monotherapy. The primary end points were the incidence of cutaneous squamous-cell carcinoma, survival free of melanoma progression, and response. Secondary end points were overall survival and pharmacokinetic activity.
Dose-limiting toxic effects were infrequently observed in patients receiving combination therapy with 150 mg of dabrafenib and 2 mg of trametinib (combination 150/2). Cutaneous squamous-cell carcinoma was seen in 7% of patients receiving combination 150/2 and in 19% receiving monotherapy (P=0.09), whereas pyrexia was more common in the combination 150/2 group than in the monotherapy group (71% vs. 26%). Median progression-free survival in the combination 150/2 group was 9.4 months, as compared with 5.8 months in the monotherapy group (hazard ratio for progression or death, 0.39; 95% confidence interval, 0.25 to 0.62; P<0.001). The rate of complete or partial response with combination 150/2 therapy was 76%, as compared with 54% with monotherapy (P=0.03).
Dabrafenib and trametinib were safely combined at full monotherapy doses. The rate of pyrexia was increased with combination therapy, whereas the rate of proliferative skin lesions was nonsignificantly reduced. Progression-free survival was significantly improved. (Funded by GlaxoSmithKline; ClinicalTrials.gov number, NCT01072175.).
Resistance to endocrine therapy in breast cancer is associated with activation of the mammalian target of rapamycin (mTOR) intracellular signaling pathway. In early studies, the mTOR inhibitor ...everolimus added to endocrine therapy showed antitumor activity.
In this phase 3, randomized trial, we compared everolimus and exemestane versus exemestane and placebo (randomly assigned in a 2:1 ratio) in 724 patients with hormone-receptor-positive advanced breast cancer who had recurrence or progression while receiving previous therapy with a nonsteroidal aromatase inhibitor in the adjuvant setting or to treat advanced disease (or both). The primary end point was progression-free survival. Secondary end points included survival, response rate, and safety. A preplanned interim analysis was performed by an independent data and safety monitoring committee after 359 progression-free survival events were observed.
Baseline characteristics were well balanced between the two study groups. The median age was 62 years, 56% had visceral involvement, and 84% had hormone-sensitive disease. Previous therapy included letrozole or anastrozole (100%), tamoxifen (48%), fulvestrant (16%), and chemotherapy (68%). The most common grade 3 or 4 adverse events were stomatitis (8% in the everolimus-plus-exemestane group vs. 1% in the placebo-plus-exemestane group), anemia (6% vs. <1%), dyspnea (4% vs. 1%), hyperglycemia (4% vs. <1%), fatigue (4% vs. 1%), and pneumonitis (3% vs. 0%). At the interim analysis, median progression-free survival was 6.9 months with everolimus plus exemestane and 2.8 months with placebo plus exemestane, according to assessments by local investigators (hazard ratio for progression or death, 0.43; 95% confidence interval CI, 0.35 to 0.54; P<0.001). Median progression-free survival was 10.6 months and 4.1 months, respectively, according to central assessment (hazard ratio, 0.36; 95% CI, 0.27 to 0.47; P<0.001).
Everolimus combined with an aromatase inhibitor improved progression-free survival in patients with hormone-receptor-positive advanced breast cancer previously treated with nonsteroidal aromatase inhibitors. (Funded by Novartis; BOLERO-2 ClinicalTrials.gov number, NCT00863655.).
Lower grade gliomas (LGGs) are malignant brain tumors. Current therapy is associated with short- and long-term toxicity. Progression to higher tumor grade is associated with contrast enhancement on ...MRI. The majority of LGGs harbor mutations in the genes encoding isocitrate dehydrogenase 1 or 2 (
). Vorasidenib (AG-881) is a first-in-class, brain-penetrant, dual inhibitor of the mutant IDH1 and mutant IDH2 enzymes.
We conducted a multicenter, open-label, phase I, dose-escalation study of vorasidenib in 93 patients with mutant
(m
) solid tumors, including 52 patients with glioma that had recurred or progressed following standard therapy. Vorasidenib was administered orally, once daily, in 28-day cycles until progression or unacceptable toxicity. Enrollment is complete; this trial is registered with ClinicalTrials.gov, NCT02481154.
Vorasidenib showed a favorable safety profile in the glioma cohort. Dose-limiting toxicities of elevated transaminases occurred at doses ≥100 mg and were reversible. The protocol-defined objective response rate per Response Assessment in Neuro-Oncology criteria for LGG in patients with nonenhancing glioma was 18% (one partial response, three minor responses). The median progression-free survival was 36.8 months 95% confidence interval (CI), 11.2-40.8 for patients with nonenhancing glioma and 3.6 months (95% CI, 1.8-6.5) for patients with enhancing glioma. Exploratory evaluation of tumor volumes in patients with nonenhancing glioma showed sustained tumor shrinkage in multiple patients.
Vorasidenib was well tolerated and showed preliminary antitumor activity in patients with recurrent or progressive nonenhancing m
LGG.
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