Pharmacotherapeutic Group: Antineoplastic agent.
ATC Code: L01 XC03.
Pharmacology: Pharmacodynamics: Mechanism of Action: Trastuzumab is a recombinant humanised monoclonal antibody that selectively targets the extracellular domain of the human epidermal growth factor receptor 2 protein (HER2). The antibody is an IgG
1 isotype that contains human framework regions with the complementarity-determining regions of a murine anti-p185 HER2 antibody that binds to human HER2.
The HER2 proto-oncogene or c-erbB2 encodes for a single transmembrane spanning, receptor-like protein of 185 kDa, which is structurally related to the epidermal growth factor receptor. Overexpression of HER2 is observed in 15%-20% of primary breast cancer. The overall rate of HER2 positivity in advanced gastric cancers as observed during screening for study BO18255 is 15% for IHC3+ and IHC2+/FISH+ or 22.1% when applying the broader definition of IHC3+ or FISH+. A consequence of HER2 gene amplification is an increase in HER2 protein expression on the surface of these tumour cells, which results in a constitutively activated HER2 protein.
Studies indicate that breast cancer patients whose tumours have amplification or overexpression of HER2 have a shortened disease-free survival compared to patients whose tumours do not have amplification or overexpression of HER2.
Trastuzumab has been shown, both in in-vitro assays and in animals, to inhibit the proliferation of human tumour cells that overexpress HER2. In vitro, trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) has been shown to be preferentially exerted on HER2 overexpressing cancer cells compared with cancer cells that do not overexpress HER2.
Clinical/Efficacy Studies: Metastatic Breast Cancer: Herceptin monotherapy has been used in clinical trials for patients with metastatic breast cancer who have tumours that overexpress HER2 and who have failed one or more chemotherapy regimens for their metastatic disease.
Herceptin has also been used in clinical trials in combination with paclitaxel or an anthracycline (doxorubicin or epirubicin) plus cyclophosphamide as first line therapy for patients with metastatic breast cancer who have tumours that overexpress HER2.
Patients who had previously received anthracycline-based adjuvant chemotherapy were treated with paclitaxel (175 mg/m
2 infused over 3 hours) with or without Herceptin. Patients could be treated with Herceptin until progression of disease.
Herceptin monotherapy, when used as second- or third-line treatment of women with metastatic breast cancer which overexpresses HER2, results in an overall tumour response rate of 15% and a median survival of 13 months.
The use of Herceptin in combination with paclitaxel as first-line treatment of women with metastatic breast cancer that overexpresses HER2 significantly prolongs the median time to disease progression, compared with patients treated with paclitaxel alone. The increase in median time to disease progression for patients treated with Herceptin and paclitaxel is 3.9 months (6.9 months versus. 3.0 months). Tumour response and one year survival rate are also increased for Herceptin in combination with paclitaxel versus paclitaxel alone.
Herceptin has also been studied in a randomised, controlled trial, in combination with docetaxel, as first-line treatment of women with metastatic breast cancer. The combination of Herceptin and docetaxel significantly increased response rate (61% versus 34%) and prolonged the median time to disease progression (by 5.6 months), compared with patients treated with docetaxel alone. Median survival was also significantly increased in patients receiving the combination, compared with those receiving docetaxel alone (31.2 months versus 22.7 months).
Combination treatment with Herceptin and anastrozole: Herceptin has been studied in combination with anastrozole for first line treatment of metastatic breast cancer in HER2 overexpressing, hormone-receptor [i.e. oestrogen-receptor (ER) and/or progesterone-receptor (PR)] positive patients. Progression free survival was doubled in the Herceptin plus anastrozole arm compared to anastrozole (4.8 months versus 2.4 months). For the other parameters the improvements seen for the combination were; for overall response (16.5% versus 6.7%); clinical benefit rate (42.7% versus 27.9%); time to progression (4.8 months versus 2.4 months). For time to response and duration of response no difference could be recorded between the arms. The median overall survival was extended by 4.6 months for patients in the combination arm. The difference was not statistically significant, however more than half of the patients in the anastrozole alone arm crossed over to a Herceptin containing regimen after progression of disease. Fifty two percent of the patients taking Herceptin plus anastrozole survived for at least 2 years compared to 45% taking anastrozole alone.
Early Breast Cancer: In the adjuvant treatment setting, Herceptin was investigated in 4 large multicentre, randomised, phase 3 trials: Study BO16348 was designed to compare one and two years of three-weekly Herceptin treatment versus observation in patients with HER2-positive early breast cancer following surgery, established chemotherapy and radiotherapy (if applicable). In addition, a comparison of two years of Herceptin treatment versus one year of Herceptin treatment was performed. Patients assigned to receive Herceptin were given an initial loading dose of 8 mg/kg, followed by 6 mg/kg every three weeks for either one or two years.
Studies NSABP B-31 and NCCTG N9831 that comprise the joint analysis were designed to investigate the clinical utility of combining Herceptin IV treatment with paclitaxel following AC chemotherapy; additionally the NCCTG N9831 study investigated adding Herceptin sequentially to AC-paclitaxel chemotherapy in patients with HER2-positive early breast cancer following surgery.
Study BCIRG 006 was designed to investigate combining Herceptin IV treatment with docetaxel either following AC chemotherapy or in combination with docetaxel and carboplatin in patients with HER2-positive early breast cancer following surgery.
Early breast cancer in the BO16348 study was limited to operable, primary, invasive adenocarcinoma of the breast, with axillary nodes-positive or axillary nodes-negative tumours of at least 1 cm in diameter.
The efficacy results from the BO16348 study are summarized in the following table: see Table 1.
Click on icon to see table/diagram/image
The efficacy results from the interim efficacy analysis crossed the protocol pre-specified statistical boundary for the comparison of 1-year of Herceptin vs. observation. After a median follow-up of 12 months, the hazard ratio (HR) for disease free survival (DFS) was 0.54 (95% CI 0.44, 0.67) which translates into an absolute benefit, in terms of a 2-year disease-free survival rate, of 7.6 percentage points (85.8% versus 78.2%) in favour of the Herceptin arm.
A final analysis was performed after a median follow-up of 8 years, which showed that 1 year Herceptin treatment is associated with a 24% risk reduction compared to observation only (HR=0.76, 95% CI 0.67, 0.86). This translates into an absolute benefit in terms of an 8 year disease free survival rate of 6.4 percentage points in favour of 1 year Herceptin treatment.
In this final analysis, extending Herceptin treatment for a duration of two years did not show additional benefit over treatment for 1 year [DFS HR in the intent to treat (ITT) population of 2 years vs 1 year=0.99 (95% CI: 0.87, 1.13), p-value=0.90 and OS HR=0.98 (0.83, 1.15); p-value=0.78]. The rate of asymptomatic cardiac dysfunction was increased in the 2-year treatment arm (8.1% versus 4.6% in the 1-year treatment arm). More patients experienced at least one grade 3 or 4 adverse event in the 2-year treatment arm (20.4%) compared with the 1-year treatment arm (16.3%).
In the joint analysis of the NSABP B-31 and NCCTG N9831 studies, early breast cancer was limited to women with operable breast cancer at high risk, defined as HER2-positive and axillary lymph node-positive or HER2-positive and lymph node-negative with high risk features (tumour size > 1 cm and ER negative or tumour size > 2 cm, regardless of hormonal status). Herceptin was administered in combination with paclitaxel, following AC chemotherapy. Paclitaxel was administered as follows: intravenous paclitaxel - 80 mg/m
2 as a continuous IV infusion, given every week for 12 weeks, or; intravenous paclitaxel - 175 mg/m
2 as a continuous IV infusion, given every 3 weeks for 4 cycles (day 1 of each cycle). (See Table 2.)
Click on icon to see table/diagram/image
For the primary endpoint, DFS, the addition of Herceptin to paclitaxel chemotherapy resulted in a 52% decrease in the risk of disease recurrence. The hazard ratio translates into an absolute benefit, in terms of a 3-year disease-free survival rate, of 11.8 percentage points (87.2% versus 75.4%) in favour of the AC→PH (Herceptin) arm.
The pre-planned final analysis of OS from the joint analysis of studies NSABP B-31 and NCCTG N9831 was performed when 707 deaths had occurred (median follow-up 8.3 years in the AC→P H group). Treatment with AC→PH resulted in a statistically significant improvement in OS compared with AC→P (stratified HR=0.64; 95% CI [0.55, 0.74]; log-rank p-value < 0.0001). At 8 years, the survival rate was estimated to be 86.9% in the AC→PH arm and 79.4% in the AC→P arm, an absolute benefit of 7.4% (95% CI 4.9%, 10.0%).
The final OS results from the joint analysis of studies NSABP B-31 and NCCTG N9831 are summarized in the following table: see Table 3.
Click on icon to see table/diagram/image
In the BCIRG 006 study, HER2-positive, early breast cancer was limited to either lymph node-positive or high risk node-negative patients, defined as negative (pN0) lymph node involvement, and at least 1 of the following factors: tumour size greater than 2 cm, oestrogen receptor and progesterone receptor negative, histologic and/or nuclear grade 2 - 3, or age < 35 years. Herceptin was administered either in combination with docetaxel, following AC chemotherapy (AC-DH) or in combination with docetaxel and carboplatin (DCarbH).
Docetaxel was administered as follows: intravenously (100 mg/m
2 as an IV infusion over 1 hour) given every 3 weeks for 4 cycles (day 2 of first docetaxel cycle, then day 1 of each subsequent cycle), or; intravenously (75 mg/m
2 as an IV infusion over 1 hour) given every 3 weeks for 6 cycles (day 2 of cycle 1, then day 1 of each cycle).
Docetaxel therapy was followed by carboplatin (at target AUC = 6 mg/ml/min) administered by IV infusion over 30-60 minutes repeated every 3 weeks for a total of 6 cycles.
The efficacy results from the BCIRG 006 study are summarized in the following tables: see Tables 4 and 5.
Click on icon to see table/diagram/image
Click on icon to see table/diagram/image
In the BCIRG 006 study for the primary endpoint, DFS, the hazard ratio translates into an absolute benefit, in terms of a 3-year disease-free survival rate, of 5.8 percentage points (86.7% versus 80.9%) in favour of the AC→DH (Herceptin) arm and 4.6 percentage points (85.5% versus 80.9%) in favour of the DCarbH (Herceptin) arm compared to AC→D.
For the secondary endpoint overall survival, treatment with AC→DH reduced the risk of death by 42% when compared to AC→D (hazard ratio 0.58 [95% CI: 0.40, 0.83] p = 0.0024, log-rank test) and the risk of death was reduced by 34% for patients treated with DCarbH compared to patients treated with AC→D (hazard ratio 0.66 [95% CI: 0.47, 0.93], p = 0.0182). In the BCIRG 006 study at the second interim analysis, 185 randomised patients had died: 80 patients (7.5%) in the AC→D arm, 49 patients (4.6%) in the AC→DH arm, and 56 patients (5.2%) in the DCarbH arm. The median duration of follow-up was 2.9 years in the AC→D arm and 3.0 years in both the AC→DH and DCarbH arms.
In the neoadjuvant-adjuvant treatment setting, Herceptin was evaluated in two phase 3 trials.
Study MO16432 investigated a total of 10 cycles of neoadjuvant chemotherapy [an anthracycline and a taxane (AP+H followed by P+H, followed by CMF+H] concurrently with neoadjuvant-adjuvant Herceptin, or neoadjuvant chemotherapy alone, followed by adjuvant Herceptin for up to a total treatment duration of 1 year) in newly diagnosed locally advanced (Stage III) or inflammatory HER2-positive breast cancer patients.
Study BO22227 was designed to demonstrate non-inferiority of treatment with Herceptin SC versus Herceptin IV based on co-primary PK and efficacy endpoints (trastuzumab C
trough at pre-dose Cycle 8, and pCR rate at definitive surgery, respectively). Patients with HER2-positive, operable or locally advanced breast cancer (LABC) including inflammatory breast cancer received eight cycles of either Herceptin IV or Herceptin SC concurrently with chemotherapy (docetaxel followed by FEC), followed by surgery, and continued therapy with Herceptin SC or Herceptin IV as originally randomised for an additional 10 cycles for a total of one year of treatment.
The efficacy results from Study MO16432 are summarized in the table as follows. The median duration of follow-up in the Herceptin arm was 3.8 years. (See Table 6.)
Click on icon to see table/diagram/image
For the primary endpoint, EFS, the addition of Herceptin to the neoadjuvant chemotherapy followed by adjuvant Herceptin for a total duration of 52 weeks resulted in a 35% reduction in the risk of disease recurrence/progression. The hazard ratio translates into an absolute benefit, in terms of 3-year event-free survival rate estimates of 13 percentage points (65% versus 52%) in favour of the Herceptin arm.
In Study BO22227 the analysis of the efficacy part of the co-primary endpoint, pCR, defined as absence of invasive neoplastic cells in the breast, resulted in rates of 40.7% (95% CI: 34.7, 46.9) in the Herceptin IV arm and 45.4% (95% CI: 39.2%, 51.7%) in the Herceptin SC arm, a difference of 4.7% in favour of the Herceptin SC arm. The lower boundary of the one-sided 97.5% confidence interval for the difference in pCR rates was -4.0, whereas the pre-defined non-inferiority margin was -12.5%, establishing the non-inferiority of Herceptin SC for the co-primary endpoint. (See Table 7.)
Click on icon to see table/diagram/image
Analyses with longer term follow-up of a median duration exceeding 40 months supported the non-inferior efficacy of Herceptin SC compared to Herceptin IV with comparable results of both EFS and OS (3-year EFS rates of 73% in the Herceptin IV arm and 76% in the Herceptin SC arm, and 3-year OS rates of 90% in the Herceptin IV arm and 92% in the Herceptin SC arm).
For non-inferiority of the PK co-primary endpoint, steady-state trastuzumab C
trough value at the end of treatment Cycle 7, refer to Pharmacology: Pharmacokinetics under Actions.
The final analysis at a median follow-up exceeding 70 months showed similar EFS and OS between patients who received Herceptin IV and those who received Herceptin SC. The 6-year EFS rate was 65% in both arms (ITT population: HR=0.98 [95% CI: 0.74;1.29]) and the OS rate, 84% in both arms (ITT population: HR=0.94 [95% CI: 0.61;1.45])
Advanced Gastric Cancer: The efficacy results from the BO18255 study are summarized in Table 8. Patients with previously untreated for HER2-positive inoperable locally advanced or recurrent and/or metastatic adenocarcinoma of the stomach or gastro-oesophageal junction not amenable to curative therapy were recruited. The primary endpoint was overall survival which was defined as the time from the date of randomization to the date of death from any cause. At the time of the analysis a total of 349 randomised patients had died: 182 patients (62.8%) in the control arm and 167 patients (56.8%) in the treatment arm. The majority of the deaths were due to events related to the underlying cancer.
The overall survival was significantly improved in the Herceptin + capecitabine/5-FU and cisplatin arm compared to the capecitabine/5-FU and cisplatin arm (p = 0.0046, log rank test). The median survival time was 11.1 months with capecitabine/5-FU and cisplatin and 13.8 months with Herceptin + capecitabine/5-FU and cisplatin. The risk of death was decreased by 26% (hazard ratio [HR] 0.74 95% CI [0.60-0.91]) for patients in the Herceptin arm compared to the capecitabine/5-FU arm.
Post-hoc subgroup analyses indicate that targeting tumours with higher levels of HER2 protein (IHC 2+/FISH+ and IHC 3+/regardless of the FISH status) results in a greater treatment effect. The median overall survival for the high HER2 expressing group was 11.8 months versus 16 months, HR 0.65 (95% CI 0.51-0.83) and the median progression-free survival was 5.5 months versus 7.6 months, HR 0.64 (95% CI 0.51-0.79) for capecitabine/5-FU and cisplatin and Herceptin + capecitabine/5-FU and cisplatin, respectively.
In a method comparison study a high degree of concordance (> 95%) was observed for SISH and FISH techniques for the detection of HER2 gene amplification in gastric cancer patients. (See Table 8.)
Click on icon to see table/diagram/image
Immunogenicity: In the neoadjuvant-adjuvant EBC study (BO22227), at a median follow-up exceeding 70 months, 10.1% (30/296) of patients treated with Herceptin IV and 15.9% (47/295) of patients receiving Herceptin SC Vial developed antibodies against trastuzumab. Neutralizing anti-trastuzumab antibodies were detected in post-baseline samples in 2 of 30 patients in the Herceptin IV arm and 3 of 47 patients in the Herceptin SC arm.
The clinical relevance of these antibodies is not known. The presence of anti-trastuzumab antibodies had no impact on pharmacokinetics, efficacy [determined by pathological complete response (pCR) and event free survival (EFS)] and safety [determined by occurrence of administration related reactions (ARRs)] of Herceptin IV and Herceptin SC.
Pharmacokinetics: Herceptin: The pharmacokinetics of trastuzumab were evaluated in a population pharmacokinetic model analysis using pooled data from 1,582 subjects from 18 Phase I, II and III trials receiving Herceptin IV. A two-compartment model with parallel linear and non-linear elimination from the central compartment described the trastuzumab concentration-time profile. Due to the non-linear elimination, total clearance increased with decreasing concentrations. Linear clearance was 0.127 L/day for breast cancer (MBC/EBC) and 0.176 L/day for AGC. The nonlinear elimination parameter values were 8.81 mg/day for the maximum elimination rate (Vmax) and 8.92 mg/L for the Michaelis-Menten constant (Km). The central compartment volume was 2.62 L for patients with breast cancer and 3.63 L for patients with AGC.
The population predicted PK exposures (with 5
th - 95
th Percentiles) and PK parameter values at clinically relevant concentrations (C
max and C
min) for breast cancer and AGC patients treated with the approved q1w and q3w dosing regimens are shown in Table 9 (Cycle 1) and Table 10 (steady-state) as follows. (See Tables 9 and 10.)
Click on icon to see table/diagram/image
Click on icon to see table/diagram/image
Herceptin SC: The pharmacokinetics of trastuzumab given as a fixed 600 mg dose of Herceptin SC Vial administered q3w were compared to those of Herceptin IV given as a weight-based 8 mg/kg loading dose followed by 6 mg/kg maintenance doses administered q3w in the phase III study BO22227. The pharmacokinetic results for the co-primary PK endpoint, trastuzumab trough concentration at pre-dose Cycle 8, showed non-inferior trastuzumab exposure for the Herceptin SC arm with fixed 600 mg q3w dosing compared to the Herceptin IV arm with body-weight adjusted q3w dosing. Analysis of Cycle 1 serum trastuzumab trough values confirmed that no loading dose is needed when using the Herceptin SC 600 mg fixed dose, in contrast to when using Herceptin IV weight-based dosing.
The mean observed trastuzumab concentration during the neoadjuvant treatment phase, at the pre-dose Cycle 8 time point, was higher in the Herceptin SC arm than in the Herceptin IV arm of the study, with mean observed values of 78.7 µg/ml (standard deviation: 43.9 µg/ml) as compared to 57.8 µg/ml (standard deviation: 30.3 µg/ml). During the adjuvant treatment phase, at the pre-dose Cycle 13 time point, the mean observed trastuzumab trough concentration values were 90.4 µg/ml (SD: 41.9 µg/ml) and 62.1 µg/ml (SD: 37.1 µg/ml) respectively for the Herceptin SC and Herceptin IV arms of the study. While approximate steady state concentrations with Herceptin IV or Herceptin SC are reached at approximately cycle 8, observed trastuzumab trough concentrations with Herceptin SC tended to increase slightly up to cycle 13. The mean observed trastuzumab trough concentration at pre-dose Cycle 18 was 90.7 µg/ml, similar to that of Cycle 13, suggesting no further increase after cycle 13.
The median T
max following Herceptin SC Cycle 7 administration was approximately 3 days, with high variability (range 1-14 days). The mean C
max was, as expected, lower in the Herceptin SC arm (149 μg/ml) than in the Herceptin IV arm (end of infusion value: 221 μg/ml).
The mean observed AUC
0-21 days value following the Cycle 7 dose was approximately 10% higher with Herceptin SC as compared to Herceptin IV, with mean AUC values of 2268 µg/ml•day and 2056 µg/ml•day respectively. With Herceptin IV and Herceptin SC, body weight had an influence on the pre-dose trastuzumab trough concentration and AUC
0-21days values. In patients with body weight (BW), below 51 kg (10th percentile), the mean steady state AUC value of trastuzumab following the Cycle 7 dose was about 80% higher after Herceptin SC than after Herceptin IV treatment, whereas in the highest BW group above 90 kg (90th percentile) the mean steady state AUC value was 20% lower after Herceptin SC than after Herceptin IV treatment. Across body weight subsets, patients who received Herceptin SC had pre-dose trastuzumab concentration and AUC
0-21days values that were comparable to or higher than those observed in patients who received Herceptin IV. Multiple logistic regression analyses showed no correlation of trastuzumab PK to efficacy (pCR) or safety (AE) outcomes, and dose adjustment for body weight is not needed.
A population PK model with parallel linear and nonlinear elimination from the central compartment was constructed using pooled trastuzumab PK data from the phase III study BO22227 of Herceptin SC vs. Herceptin IV, to describe the observed PK concentrations following Herceptin IV or Herceptin SC administration in EBC patients. Bioavailability of trastuzumab given as Herceptin SC was estimated to be 77.1%, and the first order absorption rate constant was estimated to be 0.4 day
-1.
Linear elimination clearance was 0.1111/day and the central compartment volume (V
c) was 2.911. The nonlinear elimination Michaelis-Menten parameters were 11.9 mg/day and 33.9 mg/l for V
max and Km, respectively. The population predicted PK exposure parameter values (with 5
th - 95
th Percentiles) for the Herceptin SC 600 mg q3w regimen in EBC patients is shown in Table 11 as follows. (See Table 11.)
Click on icon to see table/diagram/image
Trastuzumab washout: Trastuzumab washout time period was assessed following Herceptin IV and Herceptin SC administration using the respective population PK models. The results of these simulations indicate that at least 95% of patients will reach serum trastuzumab concentrations that are <1 μg/mL (approximately 3% of the population predicted C
min,ss, or about 97% washout) by 7 months after the last dose.
Pharmacokinetics in Special Populations: Detailed pharmacokinetic studies in the geriatric population and those with renal or hepatic impairment have not been carried out.
Renal Impairment: Detailed pharmacokinetic studies in patients with renal impairment have not been carried out. In a population pharmacokinetic analysis, renal impairment was shown not to affect trastuzumab disposition.
Geriatric Population: Age has been shown to have no effect on the disposition of trastuzumab (see Dosage & Administration).
Toxicology: Nonclinical Safety: Herceptin: Trastuzumab was well tolerated in mice (non-binding species) and Macaque monkeys (binding species) in single-dose and repeat-dose toxicity studies of up to 6 months duration, respectively. There was no evidence of acute or chronic toxicity identified.
Herceptin SC: Trastuzumab was well tolerated in rabbits (non-binding species) and cynomolgus monkeys (binding species) in single- and repeat-dose toxicity studies, respectively.
Carcinogenicity: No carcinogenicity studies have been performed to establish the carcinogenic potential of Herceptin.
Genotoxicity: No data to report.
Impairment of Fertility: Reproduction studies have been conducted in Cynomolgus monkeys at doses up to 25 times that of the weekly human maintenance dose of 2 mg/kg Herceptin IV and have revealed no evidence of impaired fertility.
Reproductive Toxicity: Reproduction studies have been conducted in Cynomolgus monkeys at doses up to 25 times that of the weekly human maintenance dose of 2 mg/kg Herceptin IV and have revealed no evidence of harm to the foetus. However, when assessing the risk of reproductive toxicity to humans, it is also important to consider the significance of the rodent form of the HER2 receptor in normal embryonic development and the embryonic death in mutant mice lacking this receptor. Placental transfer of trastuzumab during the early (days 20 - 50 of gestation) and late (days 120 - 150 of gestation) foetal development period was observed.
Other: Lactation: A study conducted in lactating Cynomolgus monkeys at doses 25 times that of the weekly human maintenance dose of 2 mg/kg Herceptin IV demonstrated that trastuzumab is secreted in the milk. The presence of trastuzumab in the serum of infant monkeys was not associated with any adverse effects on their growth or development from birth to 1 month of age.