Zongertinib specifically targets HER2 while sparing EGFR, resulting in minimal GI and skin toxicities. In contrast, Sevabertinib inhibits both HER2 and EGFR, causing significantly higher rates of diarrhea. This makes Zongertinib a better-tolerated option for patients requiring a HER2-directed TKI.
Zongertinib shows a meaningful intracranial response rate of ~44% in HER2-mutant NSCLC. This efficacy supports initiating systemic TKI therapy for patients with small, asymptomatic brain metastases and monitoring closely with short-interval scans, potentially avoiding or delaying brain radiation and its associated toxicities.
Despite both being options, experts favor the TKI zongertinib for second-line treatment of HER2-mutant NSCLC. This preference is driven by zongertinib's higher response rates (~71%) and longer progression-free survival in this setting, coupled with a better side effect profile compared to the ADC trastuzumab-deruxtecan (TDXD).
HER2-directed TKIs (like zongertinib) and ADCs (trastuzumab-deruxtecan/TDXD) have different mechanisms, and clinical data shows they are effective when used sequentially. Zongertinib works post-TDXD, and vice-versa. However, there is no evidence to support using one HER2 TKI after another has failed.
While most HER2 mutations in NSCLC occur in the tyrosine kinase domain (TKD), about 20% arise elsewhere. Current HER2 TKIs show high activity against TKD mutations but have significantly lower response rates (~30%) for non-TKD mutations, highlighting an area of unmet need for this patient subset.
For never-smokers with HER2 mutations, immunotherapy is largely ineffective and risks severe immune-related adverse events when the patient is later switched to the correct TKI. This paradigm mirrors the approach for EGFR and ALK mutations, where targeted therapy is the standard upfront, even with high PD-L1 expression.