Pharmacology: Mechanism of Action: Everolimus is a signal transduction inhibitor targeting mammalian target of rapamycin (mTOR), or more specifically, mammalian 'target of rapamycin' complex 1 (mTORC1). mTOR is a key serine-threonine kinase playing a central role in the regulation of cell growth, proliferation and survival. The regulation of mTORC1 signaling is complex, being modulated by mitogens, growth factors, energy and nutrient availability. mTORC1 is an essential regulator of global protein synthesis downstream on the PI3K/AKT pathway, which is dysregulated in the majority of human cancers.
Activation of the mTOR pathway is a key adaptive change driving endocrine resistance in breast cancer. Various signal transduction pathways are activated to escape the effect of endocrine therapy. One pathway is the P13K/Akt/mTOR pathway, which is constitutively activated in aromatase inhibitor (AI)-resistant and long-term estrogen-deprived breast cancer cells. In breast cancer cells, resistance to AIs due to Akt activation can be reversed by co-administration with everolimus.
Pharmacodynamics: Everolimus is a selective mTOR inhibitor, specifically targeting the mTOR-raptor signal transduction complex (mTORC1). mTOR is a key serine-threonine kinase in the P13K/AKT signaling cascade, a pathway known to be dysregulated in the majority of human cancers. Everolimus exerts its activity through high affinity interaction with the intracellular receptor protein FKBP12. The FKBP12/everolimus complex binds to mTORC1, inhibiting its signaling capacity. mTORC1 signaling is effected through modulation of the phosphorylation of downstream effectors, the best characterized of which are the translational regulators S6 ribosomal protein kinase (S6K1) and eukaryotic elongation factor 4E-binding protein (4E-BP). Disruption of S6K1 and 4E-BPI function, as a consequence of mTORC1 inhibition, interferes with the translation of mRNAs encoding pivotal proteins involved in cell cycle regulation, glycolysis and adaptation to low oxygen conditions (hypoxia). This inhibits tumor angiogenic processes [eg, the vascular endothelial growth factor (VEGF)]. Everolimus is a potent inhibitor of the growth and proliferation of tumor cells, endothelial cells, fibroblasts and blood vessel-associated smooth muscle cells. Consistent with the central regulatory role of mTORC1, everolimus has been shown to reduce tumor cell proliferation, glycolysis and angiogenesis in solid tumors
in vivo, and thus provides 2 independent mechanisms of inhibiting tumor growth: Direct antitumor cell activity inhibition of the tumor stromal compartment.
Clinical Studies: Hormone Receptor-Positive Advanced Breast Cancer: BOLERO-2 (study CRAD001Y2301) a randomized, double-blind, multicentre phase III study of Afinitor+exemestane versus placebo+exemestane was conducted in postmenopausal women with estrogen receptor-positive, HER 2-neu/non-amplified advanced breast cancer with recurrence or progression following prior therapy with letrozole or anastrozole. Patients were randomized in a 2:1 ratio to receive either everolimus (10 mg daily) or matching placebo in addition to open-label exemestane (25 mg daily). Randomization was stratified by documented sensitivity to prior hormonal therapy (yes vs no) and by the presence of visceral metastasis (yes vs no). Sensitivity to prior hormonal therapy was defined either (1) documented clinical benefit [complete response (CR), partial response (PR), stable disease ≥24 weeks] to at least 1 prior hormonal therapy in the advanced setting or (2) at least 24 months of adjuvant hormonal therapy prior to recurrence.
The primary endpoint for the trial was progression-free survival (PFS) evaluated by Response Evaluation Criteria in Solid Tumors (RECIST), based on the investigators (local radiology) assessment. Supportive PFS analyses were based on an independent central radiology review.
Secondary endpoints included overall survival (OS), overall response rate (ORR), clinical benefit rate (CBR),safety, change in quality of life (QoL) and time to ECOG PS deterioration. Additional endpoints included changes in bone turnover markers at 6 and 12 weeks.
A total of 724 patients were randomized in 2:1 ratio to the combination everolimus (10 mg daily)+exemestane (25 mg daily) (n=485) or placebo+exemestane arm (25 mg daily) (n=239). The 2 treatment groups were generally balanced with respect to the baseline demographics of disease characteristics and history of prior antineoplastic usages. The median age of patients was 61 years (range 28-93) and 75% were Caucasian.
The efficacy results were obtained from an interim analysis after 359 local PFS events and 217 central PFS events were observed. Patients in the placebo+exemestane arm did not crossover to everolimus at the time of progression.
The study demonstrated a statistically significant clinical benefit of everolimus+exemestane over placebo+exemestane by a 2.4-fold prolongation in median PFS (median: 6.93 months vs 2.83 months), resulting in a 57% risk reduction of progression or death (PFS HR 0.43; 95% CI: 0.35, 0.54; one-sided log-rank test p-value <0.0001 per local investigator assessment (see Table 1 and Figure 1).
The analysis of PFS based on independent central radiological assessment was supportive and showed a 2.6-fold prolongation in median progression-free survival (10.58 months vs 4.14 months), resulting in a 64% risk reduction progression or death (PFS HR 0.36; 95% CI: 0.27, 0.47; one-sided log-rank test p-value <0.0001 (see Table 1 and Figure 2) BOLERO-2-Kaplan-Meier progression-free survival curves (independent radiological review).
Objective response as per investigator assessment based on RECIST was observed in 9.5% of patients (95% CI: 7, 12.4) in the everolimus+exemestane arm versus 0.4% (95% CI: 0-2.3) in the placebo+exemestane arm versus 0.4% (95% CI: 0-2.3) in the placebo+exemestane arm (p<0.0001 for comparison between arms). Clinical benefit rate for everolimus+exemestane was 33.4% versus 18% in the control arm; p<0.0001 (see Table 1).
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Overall survival data (OS) data were not mature at the time of the interim analysis for PFS. Eighty-three (83) deaths were reported at the interim analysis, representing 10.6% and 13% of patient-deaths reported in the everolimus+exemestane and placebo+exemestane arms, respectively.
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Nine (9)-month PFS rates were 40% of patients receiving everolimus+exemestane compared with 15% in the placebo+exemestane arm at a median follow-up of 7.6 months.
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The estimated PFS treatment effect was supported by planned subgroup analysis of PFS per investigator assessment. For all analyzed subgroups, a positive treatment effect was seen with everolimus+exemestane with an estimated hazard ratio versus placebo+exemestane ranging from 0.25-0.60 (see Table 2, Figures 3 and 4). Subgroup analyses demonstrated a homogeneous and consistent treatment effect irrespective of sensitivity to prior hormonal therapy and presence of visceral metastasis, and across major demographic and prognostic subgroups.
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Tumor reduction was also evident from the corresponding waterfall plot. Results indicate that 68.1% of patients in the everolimus+exemestane arm experienced tumor shrinkage versus 28% for placebo+exemestane (see Figure 5).
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Clinically or statistically significant differences were not observed between the 2 treatment arms in terms of time to deterioration of ECOG PS (≥1 point) and median times to deterioration (≥5%) of QLQ-C30 domain scores.
Effects on Bone: There are no long-term data on the effect of everolimus on bone. Comparative data from BOLERO-2 showed marked improvement in serum bone-turnover markers during the first 12 weeks of therapy, suggesting a favorable effect on bone turnover.
Advanced Neuroendocrine Tumors of Gastrointestinal, Lung or Pancreatic Origin: RADIANT-3 (study CRAD001C2324), a randomized, double-blind, multicentre phase III study of Afinitor plus best supportive care (BSC) versus placebo plus BSC in patients with advanced pancreatic neuroendocrine tumors (pNET), demonstrated a statistically significant clinical benefit of Afinitor over placebo by a 2.4-fold prolongation in median progression-free survival PFS (11.04 months vs 4.6 months), resulting in a 65% risk reduction in PFS (HR 0.35; 95% CI: 0.27; 0.45; p<0.0001) (see Table 3 and Figure 6).
RADIANT-3 enrolled patients with advanced pNET whose disease had progressed within the prior 12 months. Patients were stratified by prior cytotoxic chemotherapy (yes/no) and by WHO performance status (0 vs 1 and 2). Treatment with somatostatin analogs was allowed as part of BSC.
The primary endpoint for the trial was PFS evaluated by RECIST (Response Evaluation Criteria in Solid Tumors). After documented radiological progression, patients could be unblinded by the investigator: Those randomized to placebo were then able to receive open-label Afinitor.
Secondary endpoints include safety, objective response rate (ORR) [complete response (CR) or partial response (PR)], response duration and overall survival OS.
In total, 410 patients were randomized 1:1 to receive either Afinitor 10 mg/day (n=207) or placebo (n=203). Demographics were well balanced (median age 58 years, 55% male, 78.5% Caucasian).
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Eighteen (18)-month PFS rates were 34.2% for Afinitor therapy compared to 8.9% for placebo.
The overall survival results are not yet mature and no statistically significant difference in OS was noted [HR=0.99 (95% CI: 0.68-1.43)]. Crossover of 72.9% (148/203) of patients from placebo to open-label Afinitor following disease progression likely confounded the detection of any treatment-related difference in OS.
RADIANT-2 (study CRAD001C2325), a randomized, double-blind, multicentre phase III study of Afinitor plus octreotide depot (Sandostatin LAR) versus placebo plus octreotide depot in patients with advanced neuroendocrine tumors (carcinoid tumor) primarily of gastrointestinal or lung origin showed evidence of clinical benefit of Afinitor over placebo by a 5.1-month prolongation in median PFS (16.43 months vs 11.33 months; HR 0.77; 95% CI: 0.59-1; p=0.026), resulting in a 23% risk reduction in primary PFS (see Table 4 and Figure 7). Although statistical significance was not reached for the primary analysis (boundary for statistical significance was p=0.0246), analyses which adjusted for informative censoring and imbalances in the 2 treatment arms showed a treatment effect in favor of everolimus.
RADIANT-2 enrolled patients with advanced neuroendocrine tumors (carcinoid tumor) primarily of gastrointestinal or lung origin whose disease had progressed within the prior 12 months and had a history of secretory symptoms. Eighty point one percent (80.1%) of the patients in the Afinitor group received somatostatin analog therapy prior to study entry compared to 77.9% in the placebo group.
The primary endpoint is PFS evaluated by RECIST. After documented radiological progression, patients could be unblinded by the investigator: Those randomized to placebo were then able to receive open-label Afinitor.
Secondary endpoints include safety, vest overall response, response duration and overall survival.
In total, 429 patients were randomized 1:1 to receive either Afinitor 10 mg/day (n=216) or placebo (n=213), in addition to octreotide depot (Sandostatin LAR, administered IM) 30 mg every 28 days. Notable imbalances were evident for several important baseline prognostic factors, mainly in favor of the placebo group.
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Additional analyses for independent radiological review which is adjusted for informative censoring and imbalances in the 2 treatment arms showed a treatment effect in favor of everolimus. Results of an additional adjusted multivariate analysis which corrected for imbalances between treatment arms yielded a HR of 0.73 (95% CI: 0.56-0.97). A cox model with Inverse Probability of Censoring Weights (IPCW) was used to address and correct for informative censoring and imbalances in baseline characteristics between the 2 study arms. The estimated HR (95% CI) from the IPCW weighted analysis was 0.60 (0.44-0.84), with 1-sided p-value=0.0014 in favor of everolimus.
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Eighteen (18)-month PFS rates were 47.2% for everolimus therapy plus octreotide depot (Sandostatin LAR) compared with 37.4% for placebo plus octreotide depot (Sandostatin LAR).
The overall survival results are not yet mature and no statistically significant difference in OS was noted [HR for pre-specified adjusted analysis=1 (95% CI: 0.76-1.133)]. Crossover of 58.2% (124/213) of patients from placebo to open-label Afinitor following disease progression likely confounded the detection of any treatment-related difference in OS.
Advanced Renal Cell Carcinoma: RECORD-1 (CRAD001C2240), a phase III, international, multicentre, randomized, double-blind study comparing Afinitor 10 mg/day and placebo, both in conjunction with best supportive care, was conducted in patients with metastatic renal cell carcinoma whose disease had progressed despite prior treatment with VEGFR-TK1 (vascular endothelial growth factor receptor tyrosine kinase inhibitor) therapy (sunitinib, sorafenib or both sunitinib and sorafenib). Prior therapy with bevacizumab and interferon-α was also permitted. Patients were stratified according to Memorial Sloan-Kettering Cancer Center (MSKCC) prognostic score (favourable-vs intermediate-vs poor-risk groups) and prior anticancer therapy (1 vs 2 prior VEGFR-TKIs).
Progression-free survival, documented using RECIST (Response Evaluation Criteria in Solid Tumors) and assessed via a blinded, independent central review, was the primary endpoint. Secondary endpoints included safety, objective tumor response rate, overall survival, disease-related symptoms and quality of life. After documented radiological progression, patients could be unblinded by the investigator: Those randomized to placebo were then able to receive open-label Afinitor 10 mg/day. The Independent Data Monitoring Committee (IDMC) recommended termination of this trial at the time of the 2nd interim analysis as the primary endpoint had been met.
In total, 416 patients were randomized 2:1 to receive Afinitor (n=277) or placebo (n=139). Demographics were well balanced [pooled median age 61 years (range 27-85), 77% male, 88% Caucasian, 74% one prior VEGFR-TK1 therapy].
Results from a planned interim analysis showed that Afinitor was superior to placebo for the primary endpoint of progression-free survival, with a statistically significant 67% reduction in the risk of progression or death (see Table 5 and Figure 8).
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Six (6)-month PFS rates were 36% for Afinitor therapy compared with 9% for placebo.
Confirmed objective tumor responses were observed in 5 patients (2%) receiving Afinitor while none were observed in patients receiving placebo. The progression-free survival advantage, therefore, primarily reflects the population with disease stabilization (corresponding to 67% of the Afinitor treatment group).
No statistically significant treatment-related difference in overall survival was noted, although there was a trend in favour of Afinitor (HR 0.82; 95% CI: 0.57-1.17; p=0.137). Crossover to open-label Afinitor following disease progression for patients allocated to placebo confounded the detection of any treatment-related difference in overall survival.
A strong trend is evident supporting better quality of life among patients receiving Afinitor as measured by disease-related symptoms (HR 075; 95% CI: 0.53-1.06; p=0.053).
Pharmacokinetics: Absorption: In patients with advanced solid tumor, peak everolimus concentrations are reached 1-2 hrs after administration of an oral dose of everolimus 5-70 mg under fasting conditions or with a light fat-free snack. C
max is dose-proportional between 5-10 mg in the daily and weekly regimens. At doses of ≥20 mg/week, the increase in C
max is less than dose-proportional, however, AUC shows dose-proportionality over the 5-70 mg dose range.
Food Effect: In healthy subjects, high-fat meals reduced systemic exposure to Afinitor 10 mg (as measured by AUC) by 22% and the peak plasma concentration C
max by 54%. Light fat meals reduced AUC by 32% and C
max by 42%. Food, however, had no apparent effect on the post-absorption phase concentration-time profile.
Distribution: The blood-to-plasma ratio of everolimus, which is concentration-dependent over the range of 5-5000 ng/mL, is 17-73%. The amount of everolimus confined to the plasma is approximately 20% at blood concentrations observed in cancer patients given Afinitor 10 mg/day. Plasma protein-binding is approximately 74% both in healthy subjects and in patients with moderate hepatic impairment.
Following IV administration in a rat model, everolimus was shown to cross the blood-brain barrier in a non-linear dose-dependent manner, suggesting saturation of an efflux pump at the blood-brain barrier. Brain penetration of everolimus has also been demonstrated in rats receiving oral doses of everolimus.
Metabolism: Everolimus is a substrate of CYP3A4 and PgP. Following oral administration, it is the main circulating component in human blood. Six (6) main metabolites of everolimus have been detected in human blood, including 3 monohydroxylated metabolites, 2 hydrolytic ring-opened products and a phosphatidylcholine conjugate of everolimus. These metabolites were also identified in animal species used in toxicity studies and showed approximately 100 times less activity than everolimus itself. Hence, the parent substance is considered to contribute the majority of the overall pharmacological activity of everolimus.
Excretion: No specific excretion studies have been undertaken in cancer patients; however, data are available from the transplantation setting. Following the administration of a single dose of radiolabelled everolimus in conjunction with ciclosporin, 80% of the radioactivity was recovered from the faeces, while 5% was excreted in the urine. The parent substance was not detected in urine or faeces.
Steady-State Pharmacokinetics: After daily or weekly administration of everolimus in patients with advanced solid tumours, steady-state AUC
0-τ was dose-proportional over the range of 5-10 mg in the daily dosing regimen and 5-70 mg on the weekly regimen. Steady state was achieved within 2 weeks with the daily dosing regimen. C
max is dose-proportional between 5 and 10 mg on the daily and weekly regimens. At doses of ≥20 mg/week, the increase in C
max is less than dose-proportional. T
max occurs at 1-2 hrs post-dose. There was a significant correlation between AUC
0-τ and pre-dose trough concentration at steady state on the daily regimen. The mean elimination half-life of everolimus is approximately 30 hrs.
Patients with Hepatic Impairment: The safety, tolerability and pharmacokinetics of Afinitor were evaluated in a single oral dose study of everolimus in 34 subjects with impaired hepatic function relative to subjects with normal hepatic function. Compared to normal subjects, there was a 1.6-fold, 3.3-fold and 3.6-fold increase in exposure [ie, AUC
(0-∞)] for subjects with mild (Child-Pugh A), moderate (Child-Pugh B) and severe (Child-Pugh C) hepatic impairment, respectively. Simulations of multiple dose pharmacokinetics support the dosing recommendations in hepatic impaired subjects based on their Child-Pugh status. Dose adjustment is recommended for patients with hepatic impairment (see Dosage & Administration and Precautions).
Patients with Renal Impairment: In a population pharmacokinetic analysis of 170 patients with advanced cancer, no significant influence of creatinine clearance (25-178 mL/min) was detected on CL/F of everolimus. Post-transplant renal impairment (creatinine clearance range 11-107 mL/min) did not affect the pharmacokinetics of everolimus in transplant patients.
Paediatric Patients: There is no indication for use of Afinitor in the paediatric cancer population (see Dosage & Administration).
Elderly Patients: In a population pharmacokinetic evaluation in cancer patients, no significant influence of age (27-85 years) on oral clearance (CL/F: range 4.8-54.5 L/hr) of everolimus was detected.
Ethnicity: Oral clearance (CL/F) is similar in Japanese and Caucasian cancer patients with similar liver functions.
Based on analysis of population pharmacokinetics, oral clearance (CL/F) is on average 20% higher in black transplant patients.
Exposure-Response Relationships: There was a moderate correlation between the decrease in the phosphorylation of 4E-BP1 (P4E-BP1) in tumor tissue and the average everolimus C
min at steady state in blood after daily administration of 5 or 10 mg everolimus. Further data suggest that the inhibition of phosphorylation of the S6 kinase is very sensitive to the mTOR inhibition by everolimus. Inhibition of phosphorylation of elF-4G was complete at all C
min values after the 10 mg daily dose.
A trend suggestive of longer progression-free survival with higher time-normalized everolimus C
min was evident in patients with advanced pancreatic neuroendocrine tumors (pNET, risk ratio 0.73; 95% CI: 0.50-1.08) and in patients with advanced carcinoid tumor (risk ratio 0.66; 95% CI: 0.40-1.08). Everolimus C
min impacted the probability of tumor size reduction (p<0.001) with the odds ratios of 1.62 and 1.46, respectively, for a change in exposure from 5 ng/mL to 10 ng/mL in patients with advanced pNET and in patients with advanced carcinoid tumor.
Toxicology: Nonclinical Safety Data: The preclinical safety profile of everolimus was assessed in mice, rats, mini pigs, monkeys and rabbits. The major target organs were male and female reproductive systems (testicular tubular degeneration, reduced sperm content in epididymides and uterine atrophy) in several species; lungs (increased alveolar macrophages) in rats and mice; and eyes (lenticular anterior suture line opacities) in rats only. Minor kidney changes were seen in the rat (exacerbation of age-related lipofuscin in tubular epithelium, increases in hydronephrosis) and mouse (exacerbation of background lesions). There was no indication of kidney toxicity in monkeys or mini pigs.
Everolimus appeared to spontaneously exacerbate background diseases (chronic myocarditis in rats, coxsackie virus infection of plasma and heart in monkeys, coccidian infestation of the gastrointestinal tract in mini pigs, skin lesions in mice and monkeys). These findings were generally observed at systemic exposure levels within the range of therapeutic exposure or above, with the exception of the findings in rats, which occurred below therapeutic exposure due to a high tissue distribution.
In a male fertility study in rats, testicular morphology was affected at ≥0.5 mg/kg, and sperm motility, sperm head count and plasma testosterone levels were diminished at 5 mg/kg, which is within the range of therapeutic exposure (52 ng·hr/mL and 414 ng·hr/mL, respectively, compared to 560 ng·hr/mL human exposure at 10 mg/day) and which caused a reduction in male fertility. There was evidence of reversibility.
Female fertility was not affected but everolimus crossed the placenta and was toxic to the conceptus. In rats, everolimus caused embryo/foetotoxicity at systemic exposure below the therapeutic level. This was manifested as mortality and reduced foetal weight. The incidence of skeletal variations and malformations (eg, sternal cleft) was increased at 0.3 and 0.9 mg/kg. In rabbits, embryotoxicity was evident in an increase in late resorptions.
In juvenile rat toxicity studies at doses as low as 0.15 mg/kg/day, systemic toxicity included decreased body weight gain and food consumption and delayed attainment of some developmental landmarks at all doses, with full or partial recovery after cessation of dosing. With the possible exception of the rat-specific lens finding (where young animals appeared to be more susceptible, it appears that there is no significant difference in the sensitivity of juvenile animals to the adverse effects of everolimus as compared to adult animals at doses of 0.5-5 mg/kg/day. No relevant toxicity was evident in juvenile monkeys at doses up to 0.5 mg/kg/day for 4-weeks.
Genotoxicity studies covering relevant genotoxicity endpoints showed no evidence of clastogenic or mutagenic activity. Administration of everolimus for up to 2 years did not indicate any oncogenic potential in mice and rats up to the highest doses, corresponding respectively to 3.9 and 0.2 times the estimated clinical exposure from a 10-mg daily dose.