| Pharmacotherapeutic group: Protein kinase inhibitors; ATC code: L01XE02 Mechanism of action and pharmacodynamic effects The epidermal growth factor (EGF) and its receptor (EGFR [HER1; ErbB1]) have been identified as key drivers in the process of cell growth and proliferation for normal and cancer cells. EGFR activating mutation within a cancer cell is an important factor in promotion of tumour cell growth, blocking of apoptosis, increasing the production of angiogenic factors and facilitating the processes of metastasis.Gefitinib is a selective small molecule inhibitor of the epidermal growth factor receptor tyrosine kinase and is an effective treatment for patients with tumours with activating mutations of the EGFR tyrosine kinase domain regardless of line of therapy. No clinically relevant activity has been shown in patients with known EGFR mutation-negative tumours.Clinical efficacy and safety First line treatment The randomised phase III first line IPASS study was conducted in patients in Asia1 with advanced (stage IIIB or IV) NSCLC of adenocarcinoma histology who were ex-light smokers (ceased smoking > 15 years ago and smoked < 10 pack years) or never smokers (see Table 2).1China, Hong Kong, Indonesia, Japan, Malaysia, Philippines, Singapore, Taiwan and Thailand.Table 2 Efficacy outcomes for gefitinib versus carboplatin/paclitaxel from the IPASS study | Population | N | Objective response rates (ORR) and 95 % CI for difference between treatmentsa | Primary endpointProgression free survival (PFS)ab | Overall survivalabc | | Overall
| 1217
| 43.0 % vs 32.2 %
[5.3 %, 16.1 %]
| HR 0.74
[0.65, 0.85]
5.7 m vs 5.8 m
p<0.0001
| HR 0.90
[0.79, 1.02]
18.8 m vs 17. 4m
p=0.1087
| | EGFR mutation-positive
| 261
| 71.2 % vs 47.3 %
[12.0 %, 34.9 %]
| HR 0.48
[0.36, 0.64]
9.5 m vs 6.3 m
p<0.0001
| HR 1.00
[0.76, 1.33]
21.6 m vs 21.9 m
| | EGFR mutation-negative
| 176
| 1.1 % vs 23.5 %
[-32.5 %, -13.3 %]
| HR 2.85
[2.05, 3.98]
1.5 m vs 5.5 m
p<0.0001
| HR 1.18
[0.86, 1.63]
11.2 m vs 12.7 m
| | EGFR mutation-unknown
| 780
| 43.3 % vs 29.2 %
[7.3 %, 20.6 %]
| HR 0.68
[0.58 to 0.81]
6.6 m vs 5.8 m
p<0.0001
| HR 0.82
[0.70 to 0.96] 18.9 m vs. 17.2 m
|
| a
| Values presented are for IRESSA versus carboplatin/paclitaxel.
| | b
| m is medians in months. Numbers in square brackets are 95 % confidence intervals for HR
| | N
| Number of patients randomised.
| | HR
| Hazard ratio (hazard ratios <1 favour IRESSA)
| Quality of life outcomes differed according to EGFR mutation status. In EGFR mutation-positive patients, significantly more IRESSA-treated patients experienced an improvement in quality of life and lung cancer symptoms vs carboplatin/paclitaxel (see Table 3).Table 3 Quality of life outcomes for gefitinib versus carboplatin/paclitaxel from the IPASS study | Population | N | FACT-L QoL improvement rate a % | LCS symptom improvement rate a% | | Overall
| 1151
| (48.0 % vs 40.8 %)
p=0.0148
| (51.5 % vs 48.5 %)
p=0.3037
| | EGFR mutation-positive
| 259
| (70.2 % vs 44.5 %)
p<0.0001
| (75.6 % vs 53.9 %)
p=0.0003
| | EGFR mutation-negative
| 169
| (14.6 % vs 36.3 %)
p=0.0021
| (20.2 % vs 47.5 %)
p=0.0002
| Trial outcome index results were supportive of FACT-L and LCS resultsa Values presented are for IRESSA versus carboplatin/paclitaxel. | N
| Number of patients evaluable for quality of life analyses
| | QoL
| Quality of life
| | FACT-L
| Functional assessment of cancer therapy-lung
| | LCS
| Lung cancer subscale
| In the IPASS trial, IRESSA demonstrated superior PFS, ORR, QoL and symptom relief with no significant difference in overall survival compared to carboplatin/paclitaxel in previously untreated patients, with locally advanced or metastatic NSCLC, whose tumours harboured activating mutations of the EGFR tyrosine kinase.Pretreated Patients The randomised phase III INTEREST study was conducted in patients with locally advanced or metastatic NSCLC who had previously received platinum-based chemotherapy. In the overall population, no statistically significant difference between gefitinib and docetaxel (75 mg/m2) was observed for overall survival, progression free survival and objective response rates (see table 4).Table 4 Efficacy outcomes for gefitinib versus docetaxel from the INTEREST study | Population | N | Objective response rates and 95 % CI for difference between treatmentsa | Progression free survivalab | Primary endpoint overall survivalab | | Overall
| 1466
| 9.1 % vs 7.6 %
[-1.5 %, 4.5 %]
| HR 1.04
[0.93,1.18]
2.2 m vs 2.7 m
p=0.4658
| HR 1.020
[0.905, 1.150] c7.6 m vs 8.0 m
p=0.7332
| | EGFR mutation-positive
| 44
| 42.1 % vs 21.1 %
[-8.2 %, 46.0 %]
| HR 0.16
[0.05, 0.49]
7.0 m vs 4.1 m
p=0.0012
| HR 0.83
[0.41, 1.67]
14.2 m vs 16.6 m
p=0.6043
| | EGFR mutation- negative
| 253
| 6.6 % vs 9.8 %
[-10.5 %, 4.4 %]
| HR 1.24
[0.94,1.64]
1.7 m vs 2.6 m
p=0.1353
| HR 1.02
[0.78, 1.33]
6.4 m vs 6.0 m
p=0.9131
| | Asiansc | 323
| 19.7 % vs 8.7 %
[3.1 %, 19.2 %]
| HR 0.83
[0.64,1.08]
2.9 m vs 2.8 m
p=0.1746
| HR 1.04
[0.80, 1.35]
10.4 m vs 12.2 m
p=0.7711
| | Non-Asians
| 1143
| 6.2 % vs 7.3 %
[-4.3 %, 2.0 %]
| HR 1.12
[0.98, 1.28]
2.0 m vs 2.7 m
p=0.1041
| HR 1.01
[0.89, 1.14]
6.9 m vs 6.9 m
p=0.9259
|
| a
| Values presented are for IRESSA versus docetaxel.
| | b
| m is medians in months. Numbers in square brackets are 96 % confidence interval for overall survival HR in the overall population, or otherwise 95 % confidence intervals for HR
| | c
| Confidence interval entirely below non-inferiority margin of 1.154
| | N
| Number of patients randomised.
| | HR
| Hazard ratio (hazard ratios <1 favour IRESSA)
|
Figures 1 and 2 Efficacy outcomes in subgroups of non-Asian patients in the INTEREST study (N patients = Number of patients randomised)  The randomised phase III ISEL study, was conducted in patients with advanced NSCLC who had received 1 or 2 prior chemotherapy regimens and were refractory or intolerant to their most recent regimen. Gefitinib plus best supportive care was compared to placebo plus best supportive care. IRESSA did not prolong survival in the overall population. Survival outcomes differed by smoking status and ethnicity (see Table 5).Table 5 Efficacy outcomes for gefitinib versus placebo from the ISEL study | Population | N | Objective response rates and 95 % CI for difference between treatmentsa | Time to treatment failureab | Primary endpoint overall survivalabc | | Overall
| 1692
| 8.0 % vs 1.3 %
[4.7 %, 8.8 %]
| HR 0.82
[0.73, 0.92]
3.0 m vs 2.6 m
p=0.0006
| HR 0.89
[0.77,1.02]
5.6 m vs 5.1 m
p=0.0871
| | EGFR mutation- positive
| 26
| 37.5 % vs 0 %
[-15.1 %, 61.4 %]
| HR 0.79
[0.20, 3.12]
10.8 m vs 3.8m
p=0.7382
| HR NC
NR vs 4.3 m
| | EGFR mutation- negative
| 189
| 2.6 % vs 0 %
[-5.6 %, 7.3 %]
| HR 1.10
[0.78, 1.56]
2.0 m vs 2.6 m
p=0.5771
| HR 1.16
[0.79, 1.72]
3.7 m vs 5.9 m
p=0.4449
| | Never smoker
| 375
| 18.1 % vs 0 %
[12.3 %, 24.0 %]
| HR 0.55
[0.42, 0.72]
5.6 m vs 2.8 m
p<0.0001
| HR 0.67
[0.49, 0.92]
8.9 m vs 6.1 m
p=0.0124
| | Ever smoker
| 1317
| 5.3 % vs 1.6 %
[1.4 %, 5.7 %]
| HR 0.89
[0.78, 1.01]
2.7 m vs 2.6 m
p=0.0707
| HR 0.92
[0.79, 1.06]
5.0 m vs 4.9 m
p=0.2420
| | Asiansd | 342
| 12.4 % vs 2.1 %
[4.0 %, 15.8 %]
| HR 0.69
[0.52, 0.91]
4.4 m vs 2.2 m
p=0.0084
| HR 0.66
[0.48, 0.91]
9.5 m vs 5.5 m
p=0.0100
| | Non-Asians
| 1350
| 6.8 % vs 1.0 %
[3.5 %, 7.9 %]
| HR 0.86
[0.76, 0.98]
2.9 m vs 2.7 m
p=0.0197
| HR 0.92
[0.80, 1.07]
5.2 m vs 5.1 m
p=0.2942
|
| a
| Values presented are for IRESSA versus placebo.
| | b
| m is medians in months. Numbers in square brackets are 95 % confidence intervals for HR
| | c
| Stratified log-rank test for overall; otherwise cox proportional hazards model
| | d
| Asian ethnicity excludes patients of Indian origin and refers to the racial origin of a patient group and not necessarily their place of birth
| | N
| Number of patients randomised
| | NC
| Not calculated for overall survival HR as the number of events is too few
| | NR
| Not reached
| | HR
| Hazard ratio (hazard ratios <1 favour IRESSA)
|
EGFR mutation status and clinical characteristics Clinical characteristics of never smoker, adenocarcinoma histology, and female gender have been shown to be independent predictors of positive EGFR mutation status in a multivariate analysis of 786 Caucasian patients from gefitinib studies* (see Table 6). Asian patients also have a higher incidence of EGFR mutation-positive tumours.Table 6 Summary of multivariate logistic regression analysis to identify factors that independently predicted for the presence of EGFR mutations in 786 Caucasian patients*| Factors that predicted for presence of EGFR mutation | p-value | Odds of EGFR mutation | Positive predictive value (9.5 % of the overall population are EGFR mutation-positive (M+)) | | Smoking status
| <0.0001
| 6.5 times higher in never smokers than ever-smokers
| 28/70 (40 %) of never smokers are M+ 47/716 (7 %) of ever smokers are M+
| | Histology
| <0.0001
| 4.4 times higher in adenocarcinoma than in non-adenocarcinoma
| 63/396 (16 %) of patients with adenocarcinoma histology are M+ 12/390 (3 %) of patients with non-adenocarcinoma histology are M+
| | Gender
| 0.0397
| 1.7 times higher in females than males
| 40/235 (17 %) of females are M+ 35/551 (6 %) of males are M+
| *from the following studies: INTEREST, ISEL, INTACT 1&2, IDEAL 1&2, INVITE | |