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Pharmacodynamics: Cardiac Electrophysiology: The effect of multiple doses of KADCYLA (3.6 mg/kg every 3 weeks) on the QTc interval was evaluated in an open label, single arm study in 51 patients with HER2-positive metastatic breast cancer. No large changes in the mean QT interval (i.e., >20 ms) were detected in the study.
Clinical Studies: Metastatic Breast Cancer: The efficacy of KADCYLA was evaluated in a randomized, multicenter, open-label trial (EMILIA) (NCT00829166) of 991 patients with HER2-positive, unresectable locally advanced or metastatic breast cancer. Prior taxane and trastuzumab-based therapy was required before trial enrollment. Patients with only prior adjuvant therapy were required to have disease recurrence during or within six months of completing adjuvant therapy. Breast tumor samples were required to show HER2 overexpression defined as 3+ IHC or FISH amplification ratio ≥2.0 determined at a central laboratory. Patients were randomly allocated (1:1) to receive lapatinib plus capecitabine or KADCYLA. Randomization was stratified by world region (United States, Western Europe, other), number of prior chemotherapy regimens for unresectable locally advanced or metastatic disease (0-1, >1) and visceral versus non-visceral disease as determined by the investigators.
KADCYLA was given intravenously at 3.6 mg/kg on Day 1 of a 21-day cycle. Lapatinib was administered at 1250 mg/day orally once per day of a 21-day cycle and capecitabine was administered at 1000 mg/m2 orally twice daily on Days 1-14 of a 21-day cycle. Patients were treated with KADCYLA or lapatinib plus capecitabine until progression of disease, withdrawal of consent, or unacceptable toxicity. At the time of the primary analysis, median time on study drug was 5.7 months (range: 0-28.4) for KADCYLA, 4.9 months (range: 0-30.8) for lapatinib, and 4.8 months (range: 0-30.4) for capecitabine.
The co-primary efficacy outcomes of the study were progression-free survival (PFS) based on tumor response assessments by an independent review committee (IRC), and overall survival (OS). PFS was defined as the time from the date of randomization to the date of disease progression or death from any cause (whichever occurred earlier). Overall survival was defined as the time from the date of randomization to the date of death from any cause. Additional outcomes included PFS (based on investigator tumor response assessments), objective response rate (ORR), duration of response and time to symptom progression.
Patient demographics and baseline tumor characteristics were balanced between treatment arms. All patients had metastatic disease at study entry. The median age was approximately 53 years (range 24-84 years), 74% were White, 18% were Asian and 5% were Black. All but 5 patients were women. Twenty-seven percent of patients were enrolled in United States, 32% in Europe and 16% in Asia. Tumor prognostic characteristics including hormone receptor status (positive: 55%, negative: 43%), presence of visceral disease (68%) and non-visceral disease only (33%) and the number of metastatic sites (<3: 61%, ≥3: 37%) were similar in the study arms.
The majority of patients (88%) had received prior systemic treatment in the metastatic setting. Twelve percent of patients had prior treatment only in the neoadjuvant or adjuvant setting and had disease relapse within 6 months of treatment. All but one patient received trastuzumab prior to study entry; approximately 85% of patients received prior trastuzumab in the metastatic setting. Over 99% percent of patients had received a taxane, and 61% of patients had received an anthracycline prior to study entry. Overall, patients received a median of 3 systemic agents in the metastatic setting. Among patients with hormone receptor-positive tumors, 44.4% received prior adjuvant hormonal therapy and 44.8% received hormonal therapy for locally advanced/metastatic disease.
The randomized trial demonstrated a statistically significant improvement in IRC-assessed PFS in the KADCYLA-treated group compared with the lapatinib plus capecitabine-treated group [hazard ratio (HR)=0.65, 95% CI: 0.55, 0.77, p <0.0001], and an increase in median PFS of 3.2 months (median PFS of 9.6 months in the KADCYLA-treated group vs. 6.4 months in the lapatinib plus capecitabine group). See Table 1 and Figure 1. The results for investigator-assessed PFS were similar to those observed for IRC-assessed PFS.
At the time of PFS analysis, 223 patients had died. More deaths occurred in the lapatinib plus capecitabine arm (26%) compared with the KADCYLA arm (19%), however the results of this interim OS analysis did not meet the pre-specified stopping boundary for statistical significance. At the time of the second interim OS analysis, 331 events had occurred. The co-primary endpoint of OS was met; OS was significantly improved in patients receiving KADCYLA (HR=0.68, 95% CI: 0.55, 0.85, p=0.0006). This result crossed the pre-specified efficacy stopping boundary (HR=0.73 or p=0.0037). The median duration of survival was 30.9 months in the KADCYLA arm vs. 25.1 months in the lapatinib plus capecitabine arm. See Table 1 and Figure 2.
A treatment benefit with KADCYLA in terms of PFS and OS was observed in patient subgroups based on stratification factors, key baseline demographic and disease characteristics, and prior treatments. In the subgroup of patients with hormone receptor-negative disease (n=426), the hazard ratios for PFS and OS were 0.56 (95% CI: 0.44, 0.72) and 0.75 (95% CI: 0.54, 1.03), respectively. In the subgroup of patients with hormone receptor-positive disease (n=545), the hazard ratios for PFS and OS were 0.72 (95% CI: 0.58, 0.91) and 0.62 (95% CI: 0.46, 0.85), respectively. In the subgroup of patients with non-measurable disease (n=205), based on IRC assessments, the hazard ratios for PFS and OS were 0.91 (95% CI: 0.59, 1.42) and 0.96 (95% CI: 0.54, 1.68), respectively; in patients with measurable disease the hazard ratios were 0.62 (95% CI: 0.52, 0.75) and 0.65 (95% CI: 0.51, 0.82), respectively. The PFS and OS hazard ratios in patients who were younger than 65 years old (n=853) were 0.62 (95% CI: 0.52, 0.74) and 0.66 (95% CI: 0.52, 0.83), respectively. In patients ≥65 years old (n=138), the hazard ratios for PFS and OS were 1.06 (95% CI: 0.68, 1.66) and 1.05 (95% CI: 0.58, 1.91), respectively. (See Table 1 and Figures 1 and 2.)
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Click on icon to see table/diagram/imageEarly Breast Cancer: KATHERINE (NCT01772472) was a randomized, multicenter, open-label trial of 1486 patients with HER2-positive, early breast cancer. Patients were required to have had neoadjuvant taxane and trastuzumab-based therapy with residual invasive tumor in the breast and/or axillary lymph nodes. Patients received radiotherapy and/or hormonal therapy concurrent with study treatment as per local guidelines. Breast tumor samples were required to show HER2 overexpression defined as 3+ IHC or ISH amplification ratio ≥2.0 determined at a central laboratory using Ventana's PATHWAY anti-HER2-/neu (4B5) Rabbit Monoclonal Primary Antibody or INFORM HER2 Dual ISH DNA Probe Cocktail assays. Patients were randomized (1:1) to receive KADCYLA or trastuzumab. Randomization was stratified by clinical stage at presentation, hormone receptor status, preoperative HER2-directed therapy (trastuzumab, trastuzumab plus additional HER2-directed agent[s]), and pathological nodal status evaluation after preoperative therapy.
KADCYLA was given intravenously at 3.6 mg/kg on Day 1 of a 21-day cycle. Trastuzumab was given intravenously at 6 mg/kg on Day 1 of a 21-day cycle. Patients were treated with KADCYLA or trastuzumab for a total of 14 cycles unless there was recurrence of disease, withdrawal of consent, or unacceptable toxicity. At the time of the major efficacy outcome analysis, median treatment duration was 10 months for both KADCYLA- and trastuzumab-treated patients. Patients who discontinued KADCYLA for reasons other than disease recurrence could complete the remainder of the planned HER2-directed therapy with trastuzumab if appropriate based on toxicity considerations and investigator discretion.
The major efficacy outcome of the study was invasive disease-free survival (IDFS). IDFS was defined as the time from the date of randomization to first occurrence of ipsilateral invasive breast tumor recurrence, ipsilateral local or regional invasive breast cancer recurrence, distant recurrence, contralateral invasive breast cancer, or death from any cause. Additional efficacy outcomes included IDFS including second primary non-breast cancer, disease free survival (DFS), and overall survival (OS).
Patient demographics and baseline tumor characteristics were generally balanced between treatment arms. The median age was approximately 49 years (range 23-80 years), 73% were White, 9% were Asian, 6% were American Indian or Alaska Native and 3% were Black or African American. Most patients (99.7%) were women. Enrollment by region was as follows: 23% in North America, 54% in Europe and 23% throughout the rest of the world. Tumor prognostic characteristics including hormone receptor status (positive: 72%, negative: 28%), clinical stage at presentation (inoperable: 25%, operable: 75%) and pathological nodal status after preoperative therapy (node positive: 46%, node negative or not evaluated: 54%) were similar across study arms.
The majority of patients (77%) had received an anthracycline-containing neoadjuvant chemotherapy regimen. Twenty percent of patients received another HER2-targeted agent in addition to trastuzumab as a component of neoadjuvant therapy; 94% of these patients received pertuzumab.
After a median follow-up of 40 months, a statistically significant improvement in IDFS was observed in patients who received KADCYLA compared with trastuzumab. The OS data were not mature at the time of the IDFS analysis (98 deaths [6.6%] occurred in 1486 patients). The efficacy results from KATHERINE are summarized in Table 2 and Figure 3.
Consistent results were observed with KADCYLA in terms of IDFS across subgroups based on stratification factors, key baseline demographic and disease characteristics, and prior treatments. (See Table 2 and Figure 3.)
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Click on icon to see table/diagram/imagePharmacokinetics: The pharmacokinetics of KADCYLA was evaluated in a phase 1 study and in a population pharmacokinetic analysis for the trastuzumab emtansine conjugate (ADC) using pooled data from 5 trials in patients with breast cancer. A linear two-compartment model with first-order elimination from the central compartment adequately describes the ADC concentration-time profile. In addition to ADC, the pharmacokinetics of total antibody (conjugated and unconjugated trastuzumab), DM1 were also determined. The population pharmacokinetic analysis of ADC suggested no difference in KADCYLA exposure based on disease status (adjuvant vs. metastatic setting). The pharmacokinetics of KADCYLA are summarized as follows.
Distribution: Maximum concentrations (Cmax) of ADC and DM1 were observed close to the end of infusion. In EMILIA, mean (SD) ADC and DM1 Cycle 1 Cmax following KADCYLA administration was 83.4 (16.5) μg/mL and 4.61 (1.61) ng/mL, respectively. In KATHERINE, mean (SD) ADC and DM1 Cycle 1 Cmax following KADCYLA administration was 72.6 (24.3) μg/mL and 4.71 (2.25) ng/mL, respectively.
In vitro, the mean binding of DM1 to human plasma proteins was 93%. In vitro, DM1 was a substrate of P-glycoprotein (P-gp).
Based on population pharmacokinetic analysis, the central volume of distribution of ADC was 3.13 L.
Metabolism: In vitro studies indicate that DM1, the small molecule component of KADCYLA, undergoes metabolism by CYP3A4/5. DM1 did not inhibit or induce major CYP450 enzymes in vitro. In human plasma, trastuzumab emtansine catabolites MCC-DM1, Lys-MCC-DM1, and DM1 were detected at low levels.
Elimination: Based on population pharmacokinetic analysis, following intravenous infusion of KADCYLA, the clearance of the ADC was 0.68 L/day and the elimination half-life (t1/2) was approximately 4 days. No accumulation of KADCYLA was observed after repeated dosing of intravenous infusion every 3 weeks.
Based on population pharmacokinetic analysis (n=671), body weight, sum of longest diameter of target lesions by RECIST, HER2 extracellular domain (ECD) concentrations, AST, albumin, and baseline trastuzumab concentrations were identified as statistically significant covariates for trastuzumab emtansine clearance. However, the magnitude of effect of these covariates on trastuzumab emtansine exposure suggests that, with the exception of body weight, these covariates are unlikely to have a clinically meaningful effect on KADCYLA exposure. Therefore, the body weight based dose of 3.6 mg/kg every 3 weeks without correction for other covariates is considered appropriate.
Effect of Renal Impairment: Based on population pharmacokinetic analysis in 668 patients, including moderate (CLcr 30-59 mL/min, n=53) and mild (CLcr 60-89 mL/min, n=254) renal impairment, indicate that pharmacokinetics of the ADC is not affected by mild to moderate renal impairment as compared to normal renal function (CLcr ≥90 mL/min, n=361). Data from only one patient with severe renal impairment (CLcr <30 mL/min) is available [see Renal Impairment under Precautions].
Effect of Hepatic Impairment: The liver is a primary organ for eliminating DM1 and DM1-containing catabolites. The pharmacokinetics of trastuzumab emtansine and DM1-containing catabolites were evaluated after the administration of 3.6 mg/kg of KADCYLA to metastatic HER2-positive breast cancer patients with normal hepatic function (n=10), mild (Child-Pugh A; n=10) and moderate (Child-Pugh B; n=8) hepatic impairment.
Plasma concentrations of DM1 and DM1-containing catabolites (Lys-MCC-DM1 and MCC-DM1) were low and comparable between patients with and without hepatic impairment.
Systemic exposures (AUC) of trastuzumab emtansine at Cycle 1 in patients with mild and moderate hepatic impairment were approximately 38% and 67% lower than that of patients with normal hepatic function, respectively. Trastuzumab emtansine exposure (AUC) at Cycle 3 after repeated dosing in patients with mild or moderate hepatic dysfunction was within the range observed in patients with normal hepatic function.
KADCYLA has not been studied in patients with severe hepatic impairment (Child-Pugh class C).
Effects of Age and Race: Based on population pharmacokinetic analysis, age (<65 [n=577]; 65-75 (n=78); >75 [n=16]) and race (Asian [n=73]; non-Asian [n=598]) do not have a clinically meaningful effect on the pharmacokinetics of trastuzumab emtansine.
Toxicology: Nonclinical Toxicology: Carcinogenesis, Mutagenesis, Impairment of Fertility: Carcinogenicity studies have not been conducted with trastuzumab emtansine.
DM1 was aneugenic or clastogenic in an in vivo single-dose rat bone marrow micronucleus assay at exposures that were comparable to mean maximum concentrations of DM1 measured in humans administered KADCYLA. DM1 was not mutagenic in an in vitro bacterial reverse mutation (Ames) assay.
Based on results from animal toxicity studies, KADCYLA may impair fertility in humans. In a single-dose toxicity study of trastuzumab emtansine in rats, degeneration of seminiferous tubules with hemorrhage in the testes associated with increased weights of testes and epididymides at a severely toxic dose level (60 mg/kg; about 4 times the clinical exposure based on AUC) were observed. The same dose in female rats resulted in signs of hemorrhage and necrosis of the corpus luteum in ovaries. In monkeys dosed with trastuzumab emtansine once every three weeks for 12 weeks (four doses), at up to 30 mg/kg (about 7 times the clinical exposure based on AUC), there were decreases in the weights of epididymides, prostate, testes, seminal vesicles and uterus, although the interpretation of these effects is unclear due to the varied sexual maturity of enrolled animals.
Animal Toxicology and/or Pharmacology: In monkeys, treatment with doses of trastuzumab emtansine up to 30 mg/kg (about 7 times the clinical exposure based on AUC) caused dose dependent axonal degeneration in the sciatic nerve with hypertrophy or hyperplasia of the Schwann cells, and axonal degeneration of the dorsal funiculus in the spinal cord. Based on the mechanism of action of the cytotoxic component DM1, there is clinical potential for neurotoxicity [see Neurotoxicity under Precautions].
