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Best of Posters - IASLC Selection - Part 1 (ID 262)
- Event: WCLC 2013
- Type: Exhibit Showcase Session
- Presentations: 1
- Coordinates: 10/29/2013, 09:55 - 10:25, Exhibit Hall, Ground Level
P1.11-032 - Results with dacomitinib (PF-00299804), an irreversible pan-HER tyrosine kinase inhibitor, in a phase II cohort of patients with HER2-mutant or amplified lung cancers (ID 2237)
09:55 - 10:25 | Author(s): H. Zhang
Dacomitinib is an oral, irreversible small molecule inhibitor of all active members of the HER (human epidermal growth factor receptor) family of tyrosine kinases: EGFR (HER1), HER2 and HER4. Dacomitinib has shown superior activity to the reversible EGFR tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib in preclinical studies of lung cancer cell lines with sensitive and resistant EGFR mutations, and superiority to gefitinib in cell-line models with a HER2 insertion mutation or amplified HER2. As part of dacomitinib’s phase II testing, we studied a cohort of patients with HER2-mutant or -amplified lung cancers.
As a cohort of a larger phase II study, we enrolled patients who had stage IIIB/IV lung cancers and either HER2 mutations or HER2 amplification ([centromere of chromosome 17]; ratio >2), any number of prior systemic chemotherapies, but no prior HER2-targeted treatment. Dacomitinib was administered at 45 mg once daily continuously, or 30 mg if the patient had no prior systemic therapy, with the option to escalate to 45 mg. Patients were evaluated every 28 days. Endpoints included progression-free survival (PFS) rate at 4 months (PFS4m), PFS, objective response rate by RECIST, duration of response, overall survival (OS), and toxicity.
30 patients with HER2-mutant (n=26) or HER2-amplified lung cancers (n=4) were enrolled. Characteristics: 15 female; 18 never smokers (60%); 11 (37%) former smokers. 25 received a 45 mg starting dose; 5 patients received 30 mg. 10 patients had received ≥3 prior systemic therapies. 73% of patients had a PFS event. PFS4m overall was 27% (95% CI: 11%–46%; HER2-mutant subgroup: 21% [95% CI: 6%–43%]). Median overall PFS was 3 months (95% CI: 2–4; HER2-mutant subgroup: 3 months [95% CI: 2–4]). Of 25 patients in the HER2-mutant subgroup evaluable for response, 3 (12%; 95% CI: 3%–31%) experienced a partial response, all with 9 base-pair insertions in HER2 exon 20. The partial response durations were 3+, 11, and 11+ months. The preliminary estimate of median OS was 10 months (95% CI: 7–21; HER2-mutant subgroup: 10 months [95% CI: 7–21]). Among the 4 patients with HER2 amplified lung cancers, no partial responses were seen and the PFS ranged from 1–5 months. Of 29 patients evaluable for toxicity, the most common treatment-related adverse events were diarrhea (90%; grade 3/4: 21%/3%), dermatitis (72%; grade 3/4: 3%/0), fatigue (52%; grade 3/4: 3%/0), and dry skin (48%; grade 3/4: 0/0). 10% of patients discontinued treatment due to adverse events.
Dacomitinib demonstrated an overall 12% objective response rate in patients with HER2-mutant lung cancers. All 3 responding patients had 9 base-pair HER2 exon 20 insertions. No responses were seen in the 4 patients with HER2-amplified lung cancers. Dacomitinib was well tolerated with manageable toxicities, consistent with the class effects of EGFR TKIs.
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