Source: European Medicines Agency (EU) Revision Year: 2020 Publisher: Amgen Europe B.V., Minervum 7061, 4817 ZK Breda, The Netherlands
Pharmacotherapeutic group: Antineoplastic agents, monoclonal antibodies
ATC code: L01XC08
Panitumumab is a recombinant, fully human IgG2 monoclonal antibody that binds with high affinity and specificity to the human EGFR. EGFR is a transmembrane glycoprotein that is a member of a subfamily of type I receptor tyrosine kinases including EGFR (HER1/c-ErbB-1), HER2, HER3, and HER4. EGFR promotes cell growth in normal epithelial tissues, including the skin and hair follicle, and is expressed on a variety of tumour cells.
Panitumumab binds to the ligand binding domain of EGFR and inhibits receptor autophosphorylation induced by all known EGFR ligands. Binding of panitumumab to EGFR results in internalisation of the receptor, inhibition of cell growth, induction of apoptosis, and decreased interleukin 8 and vascular endothelial growth factor production.
KRAS (Kirsten rat sarcoma 2 viral oncogene homologue) and NRAS (Neuroblastoma RAS viral oncogene homologue) are highly related members of the RAS oncogene family. KRAS and NRAS genes encode small, GTP-binding proteins involved in signal transduction. A variety of stimuli, including that from the EGFR activate KRAS and NRAS which in turn stimulate other intracellular proteins to promote cell proliferation, cell survival and angiogenesis.
Activating mutations in the RAS genes occur frequently in a variety of human tumours and have been implicated in both oncogenesis and tumour progression.
In vitro assays and in vivo animal studies have shown that panitumumab inhibits the growth and survival of tumour cells expressing EGFR. No anti-tumour effects of panitumumab were observed in human tumour xenografts lacking EGFR expression. The addition of panitumumab to radiation, chemotherapy or other targeted therapeutic agents, in animal studies resulted in an increase in antitumour effects compared to radiation, chemotherapy or targeted therapeutic agents alone.
Dermatological reactions (including nail effects), observed in patients treated with Vectibix or other EGFR inhibitors, are known to be associated with the pharmacologic effects of therapy (with crossreference to sections 4.2 and 4.8).
As with all therapeutic proteins, there is potential for immunogenicity. Data on the development of anti-panitumumab antibodies has been evaluated using two different screening immunoassays for the detection of binding anti-panitumumab antibodies (an ELISA which detects high-affinity antibodies, and a Biosensor Immunoassay which detects both high and low-affinity antibodies). For patients whose sera tested positive in either screening immunoassay, an in vitro biological assay was performed to detect neutralising antibodies.
As monotherapy:
In combination with irinotecan- or oxaliplatin-based chemotherapy:
The detection of antibody formation is dependent on the sensitivity and specificity of the assay. The observed incidence of antibody positivity in an assay may be influenced by several factors including assay methodology, sample handling, timing of sample collection, concomitant medicinal products and underlying disease, therefore, comparison of the incidence of antibodies to other products may be misleading.
The efficacy of Vectibix as monotherapy in patients with metastatic colorectal cancer (mCRC) who had disease progression during or after prior chemotherapy was studied in open-label, single-arm trials (585 patients) and in two randomised controlled trials versus best supportive care (463 patients) and versus cetuximab (1,010 patients).
A multinational, randomised, controlled trial was conducted in 463 patients with EGFR-expressing metastatic carcinoma of the colon or rectum after confirmed failure of oxaliplatin and irinotecancontaining regimens. Patients were randomised 1:1 to receive Vectibix at a dose of 6 mg/kg given once every two weeks plus best supportive care (not including chemotherapy) (BSC) or BSC alone. Patients were treated until disease progression or unacceptable toxicity occurred. Upon disease progression BSC alone patients were eligible to crossover to a companion study and receive Vectibix at a dose of 6 mg/kg given once every two weeks.
The primary endpoint was PFS. The study was retrospectively analysed by wild-type KRAS (exon 2) status versus mutant KRAS (exon 2) status. Tumour samples obtained from the primary resection of colorectal cancer were analysed for the presence of the seven most common activating mutations in the codon 12 and 13 of the KRAS gene. 427 (92%) patients were evaluable for KRAS status of which 184 had mutations. The efficacy results from an analysis adjusting for potential bias from unscheduled assessments are shown in the table below. There was no difference in overall survival (OS) seen in either group.
In an exploratory analysis of banked tumour specimens from this study, 11 of 72 patients (15%) with wild-type RAS tumours receiving panitumumab had an objective response compared to only 1 of 95 patients (1%) with mutant RAS tumour status. Moreover, panitumumab treatment was associated with improved PFS compared to BSC in patients with wild-type RAS tumours (HR = 0.38 [95% CI: 0.27, 0.56]), but not in patients with tumours harbouring a RAS mutation (HR = 0.98 [95% CI: 0.73, 1.31]).
The efficacy of Vectibix was also evaluated in an open-label trial in patients with wild-type KRAS (exon 2) mCRC. A total of 1,010 patients refractory to chemotherapy were randomised 1:1 to receive Vectibix or cetuximab to test whether Vectibix is non-inferior to cetuximab. The primary endpoint was OS. Secondary endpoints included PFS and objective response rate (ORR). The efficacy results for the study are presented in the table below.
Overall, the safety profile of panitumumab was similar to that of cetuximab, in particular regarding skin toxicity. However, infusion reactions were more frequent with cetuximab (13% versus 3%) but electrolyte disturbances were more frequent with panitumumab, especially hypomagnesaemia (29% versus 19%).
Among patients with wild-type RAS mCRC, PFS, OS, and ORR were improved for subjects receiving panitumumab plus chemotherapy (FOLFOX or FOLFIRI) compared with those receiving chemotherapy alone. Patients with additional RAS mutations beyond KRAS exon 2 were unlikely to benefit from the addition of panitumumab to FOLFIRI and a detrimental effect was seen with the addition of panitumumab to FOLFOX in these patients. BRAF mutations in exon 15 were found to be prognostic of worse outcome. BRAF mutations were not predictive of the outcome for panitumumab treatment in combination with FOLFOX or FOLFIRI.
The efficacy of Vectibix in combination with oxaliplatin, 5-fluorouracil (5-FU), and leucovorin (FOLFOX) was evaluated in a randomised, controlled trial of 1,183 patients with mCRC with the primary endpoint of PFS. Other key endpoints included the OS, ORR, time to response, time to progression (TTP), and duration of response. The study was prospectively analysed by tumour KRAS (exon 2) status which was evaluable in 93% of the patients.
A predefined retrospective subset analysis of 641 patients of the 656 patients with wild-type KRAS (exon 2) mCRC was performed. Patient tumour samples with wild-type KRAS exon 2 (codons 12/13) status were tested for additional RAS mutations in KRAS exon 3 (codons 61) and exon 4 (codons 117/146) and NRAS exon 2 (codons 12/13), exon 3 (codon 61), and exon 4 (codons 117/146) and BRAF exon 15 (codon 600). The incidence of these additional RAS mutations in the wild-type KRAS exon 2 population was approximately 16%.
Results in patients with wild-type RAS mCRC and mutant RAS mCRC are presented in the table below.
Additional mutations in KRAS and NRAS at exon 3 (codon 59) were subsequently identified (n = 7). An exploratory analysis showed similar results to those in the previous table.
The efficacy of Vectibix in second-line in combination with irinotecan, 5-fluorouracil (5-FU) and leucovorin (FOLFIRI) was evaluated in a randomised, controlled trial of 1,186 patients with mCRC with the primary endpoints of OS and PFS. Other key endpoints included the ORR, time to response, TTP, and duration of response. The study was prospectively analysed by tumour KRAS (exon 2) status which was evaluable in 91% of the patients.
A predefined retrospective subset analysis of 586 patients of the 597 patients with wild-type KRAS (exon 2) mCRC was performed, where tumour samples from these patients were tested for additional RAS and BRAF mutations as previously described. The RAS/BRAF ascertainment was 85% (1,014 of 1,186 randomised patients). The incidence of these additional RAS mutations (KRAS exons 3, 4 and NRAS exons 2, 3, 4) in the wild-type KRAS (exon 2) population was approximately 19%. The incidence of BRAF exon 15 mutation in the wild-type KRAS (exon 2) population was approximately 8%. Efficacy results in patients with wild-type RAS mCRC and mutant RAS mCRC are shown in the below table.
The efficacy of Vectibix in first-line in combination with FOLFIRI was evaluated in a single-arm study of 154 patients with the primary endpoint of objective response rate (ORR). Other key endpoints included the PFS, time to response, TTP, and duration of response.
A predefined retrospective subset analysis of 143 patients of the 154 patients with wild-type KRAS (exon 2) mCRC was performed, where tumour samples from these patients were tested for additional RAS mutations. The incidence of these additional RAS mutations (KRAS exons 3, 4 and NRAS exons 2, 3, 4) in the wild-type KRAS (exon 2) population was approximately 10%.
Results in patients with wild-type RAS mCRC and mutant RAS mCRC from the primary analysis are presented in the table below.
In a randomised, open-label, controlled clinical trial, chemotherapy (oxaliplatin or irinotecan) and bevacizumab were given with and without panitumumab in the first-line treatment of patients with metastatic colorectal cancer (n=1,053 [n=823 oxaliplatin cohort, n=230 irinotecan cohort]). Panitumumab treatment was discontinued due to a statistically significant reduction in PFS in patients receiving panitumumab observed in an interim analysis.
The major study objective was comparison of PFS in the oxaliplatin cohort. In the final analysis, the hazard ratio for PFS was 1.27 (95% CI: 1.06, 1.52). Median PFS was 10.0 (95% CI: 8.9, 11.0) and 11.4 (95% CI: 10.5, 11.9) months in the panitumumab and the non-panitumumab arm, respectively. There was an increase in mortality in the panitumumab arm. The hazard ratio for overall survival was 1.43 (95% CI: 1.11, 1.83). Median overall survival was 19.4 (95% CI: 18.4, 20.8) and 24.5 (95% CI: 20.4, 24.5) in the panitumumab arm and the non-panitumumab arm.
An additional analysis of efficacy data by KRAS (exon 2) status did not identify a subset of patients who benefited from panitumumab in combination with oxaliplatin- or irinotecan based chemotherapy and bevacizumab. For the wild-type KRAS subset of the oxaliplatin cohort, the hazard ratio for PFS was 1.36 with 95% CI: 1.04-1.77. For the mutant KRAS subset, the hazard ratio for PFS was 1.25 with 95% CI: 0.91-1.71. A trend for OS favouring the control arm was observed in the wild-type KRAS subset of the oxaliplatin cohort (hazard ratio = 1.89; 95% CI: 1.30, 2.75). A trend towards worse survival was also observed with panitumumab in the irinotecan cohort regardless of KRAS mutational status. Overall, panitumumab treatment combined with chemotherapy and bevacizumab is associated with an unfavourable benefit-to-risk profile irrespective of tumour KRAS mutational status.
The European Medicines Agency has waived the obligation to submit the results of studies with Vectibix in all subsets of the paediatric population in colorectal cancer (see section 4.2 for information on paediatric use).
Vectibix administered as a single agent or in combination with chemotherapy exhibits nonlinear pharmacokinetics.
Following a single-dose administration of panitumumab as a 1-hour infusion, the area under the concentration-time curve (AUC) increased in a greater than dose-proportional manner and clearance (CL) of panitumumab decreased from 30.6 to 4.6 mL/day/kg as the dose increased from 0.75 to 9 mg/kg. However, at doses above 2 mg/kg, the AUC of panitumumab increases in an approximately dose-proportional manner.
Following the recommended dose regimen (6 mg/kg given once every 2 weeks as a 1-hour infusion), panitumumab concentrations reached steady-state levels by the third infusion with mean (± Standard Deviation [SD]) peak and trough concentrations of 213 ± 59 and 39 ± 14 mcg/mL, respectively. The mean (± SD) AUC0-tau and CL were 1,306 ± 374 mcg•day/mL and 4.9 ± 1.4 mL/kg/day, respectively. The elimination half-life was approximately 7.5 days (range: 3.6 to 10.9 days).
A population pharmacokinetic analysis was performed to explore the potential effects of selected covariates on panitumumab pharmacokinetics. Results suggest that age (21-88), gender, race, hepatic function, renal function, chemotherapeutic agents, and EGFR membrane staining intensity (1+, 2+, 3+) in tumour cells had no apparent impact on the pharmacokinetics of panitumumab.
No clinical studies have been conducted to examine the pharmacokinetics of panitumumab in patients with renal or hepatic impairment.
Adverse reactions seen in animals at exposure levels similar to clinical exposure levels and with possible relevance to clinical use were as follows:
Skin rash and diarrhoea were the major findings observed in repeat-dose toxicity studies of up to 26 weeks duration in cynomolgus monkeys. These findings were observed at doses approximately equivalent to the recommended human dose and were reversible upon termination of administration of panitumumab. The skin rash and diarrhoea observed in monkeys are considered related to the pharmacological action of panitumumab and are consistent with the toxicities observed with other anti-EGFR inhibitors.
Studies to evaluate the mutagenic and carcinogenic potential of panitumumab have not been performed.
Animal studies are insufficient with respect to embryo-foetal development since foetal panitumumab exposure levels were not examined. Panitumumab has been shown to cause foetal abortions and/or foetal deaths in cynomolgus monkeys when administered during the period of organogenesis at doses approximately equivalent to the recommended human dose.
Formal male fertility studies have not been conducted; however, microscopic evaluation of male reproductive organs from repeat-dose toxicity studies in cynomolgus monkeys at doses up to approximately 5-fold the human dose on a mg/kg basis, revealed no differences compared to control male monkeys. Fertility studies conducted in female cynomolgus monkeys showed that panitumumab may produce prolonged menstrual cycle and/or amenorrhea and reduced pregnancy rate which occurred at all doses evaluated.
No pre- and post-natal development animal studies have been conducted with panitumumab. All patients should be advised regarding the potential risk of panitumumab on pre- and post-natal development prior to initiation of Vectibix therapy.
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