Click the arrow to follow us with the “blue text”!
1. 20ins Mutation: The ‘Hard-to-Treat Code’ of the EGFR Family
The EGFR exon 20 insertion (20ins) mutation accounts for 4%-12% of NSCLC. Due to the unique mutation site, traditional EGFR-TKIs (such as gefitinib and osimertinib) struggle to bind effectively, leading to its classification as a ‘blind spot’ in targeted therapy. Although amivantamab (EGFR/c-MET bispecific antibody) has become the first-line standard treatment with an objective response rate (ORR) of about 40%, there is still a lack of ideal solutions after resistance. The breakthroughs in ADCs (antibody-drug conjugates) and immunotherapy have brought new hope to this dilemma.
2. ADC: Dual Target Synergy to Precisely Break the 20ins Resistance Dilemma
The ‘hard-to-treat’ nature of the EGFR 20ins mutation arises from the spatial hindrance created by its mutation site—traditional TKIs cannot embed. While amivantamab alone has a 40% ORR and a PFS of 8.3 months, it still fails to meet the needs after resistance. The data from the BL-B01D1 study presented at the 2025 ASCO annual meeting revealed cracks in the ‘hard-to-treat’ label: among 13 treated 20ins patients, the ORR reached 85.7%, with a median tumor reduction of 42.9%, and some patients experienced relief for over 18 months. This data not only doubles that of amivantamab but also breaks the curse of ‘no effective drugs after 20ins’.
The breakthrough of BL-B01D1 stems from the design of **“dual-target lock + efficient payload”**: the EGFR/HER3 bispecific antibody simultaneously blocks two signaling pathways, avoiding single-target resistance; the Ed-04 toxin (DAR=8) is precisely released through a cleavable linker, delivering a ‘second strike’ against the HER3 bypass activated after EGFR-TKI resistance. The team from Sun Yat-sen University Cancer Prevention and Treatment Center particularly noted that in patients with baseline brain metastases, the ORR in the 300mg dose group reached 52.4%, far exceeding the 15%-20% of previous chemotherapy, indicating its potential to penetrate the blood-brain barrier.
Another TROP2 ADC, sacituzumab govitecan, breaks through with its ‘EGFR conformation-independent’ broad-spectrum efficacy. In the SKB264-II-08 study, the ORR in the 20ins subgroup reached 36.8%, with an mPFS of 9.0 months, and when combined with PD-L1 monoclonal antibodies, the ORR in first-line driver gene-negative patients exceeded 80%. Mechanistic studies found that TROP2 expression increased 3-5 times after EGFR-TKI resistance, enhancing the internalization efficiency of ADC drugs, creating a positive cycle of ‘targeted resistance – enhanced killing’. In March 2025, this drug was approved by the NMPA for treatment after EGFR-TKI resistance, becoming the first TROP2 ADC covering 20ins.
Clinical implications: The value of ADCs lies not only in efficacy numbers but also in reshaping treatment sequences—BL-B01D1 showed a PFS of 12.5 months in the chemotherapy-naive subgroup, suggesting that early intervention may delay resistance; the exploration of sacituzumab govitecan combined with chemotherapy/immunotherapy is challenging the traditional path of ’20ins must first use TKI’.
3. Immunotherapy: From ‘Marginal’ to ‘Core’ Collaborative Revolution
In the past, EGFR mutations were seen as an ‘immunological desert’, with PD-1 monotherapy ORR below 15%. However, the ‘immunogenic cell death’ effect of ADCs has completely reversed this pattern:
ADC + Immunity: Activating Cold Tumors
In the phase Ib trial of BL-B01D1 combined with PD-1, the release of tumor-associated antigens increased 4-fold, CD8+ T cell infiltration increased 2.3-fold, and the DCR rose from 92.3% with monotherapy to 97.1%. In the cohort of TROP2 ADC combined with PD-L1, the one-year OS rate for EGFR mutation patients jumped from 58% to 79%, confirming the synergistic logic of ‘targeted elimination of tumor cells + exposure of new antigens’.
New Forces of Bispecific Antibodies: Reshaping the Microenvironment
The PD-1/VEGF bispecific antibody, Ivosidenib (AK112), achieved an ORR of 68.4% in the 20ins resistant population, with a DCR of 94.7%. Its dual action of ‘anti-angiogenesis + immunity’ not only inhibits tumor neovascularization but also reverses Tregs infiltration—post-treatment tumor stroma decreased by 40%, and CD8+ T cell activity increased 3-fold, transforming ‘cold tumors’ into ‘hot tumors’. The phase III HARMONi study showed that the mPFS in the chemotherapy combination group was 6.8 months, extending 2.4 months compared to the placebo group, with more significant benefits for patients with brain metastases.
NK Cell Therapy: Filling the ADC Blind Spot
Addressing the ‘target downregulation’ issue of ADC resistance, the case of SNK01 (IL-2/IL-15 fusion protein) combined with cetuximab is encouraging: among 12 patients with dual resistance to EGFR-TKI/ADC, 11 had stable tumors, achieving a DCR of 100%. Mechanistically, NK cells compensate for the killing gap when EGFR is lowly expressed by recognizing MICA/B molecules on the surface of tumor cells, becoming a ‘supplementary weapon’ after ADC resistance.
Key Breakthrough: Immunotherapy is no longer a ‘backup’, but a collaborative partner throughout the process. For example, the phase III trial of BL-B01D1+PD-1 has been initiated, aiming to push the first-line PFS of 20ins beyond 18 months; the ‘biweekly regimen’ of sacituzumab govitecan combined with PD-L1 has an ORR as high as 82% in PD-L1 positive patients, approaching the efficacy of targeted therapy in patients with positive driver genes.
4. Future: Combination Therapy Reshaping the Treatment Path for 20ins
Currently, BL-B01D1 has entered phase III clinical trials, and if successful, it will become the first dual-target ADC for 20ins resistance. Experts consensus indicates that the combination of ADC and immunotherapy (such as BL-B01D1+PD-1) and the sequential use of ADC with fourth-generation TKIs (such as BL-B01D1 followed by PROTAC degraders) may become mainstream directions in the future. For instance, HER3-DXd still has an ORR of 29.8% after osimertinib resistance, suggesting that the ‘EGFR resistance – HER3 activation’ pathway can be precisely blocked by ADCs, while paving the way for immunotherapy.
5. Challenges and Hope Coexist
Despite the promising outlook, toxicity management (such as hematological toxicity and ILD risk of ADCs) and resistance mechanisms (such as target downregulation) remain key challenges. However, as Professor Fang Wenfeng from Sun Yat-sen University Cancer Prevention and Treatment Center emphasized at the WCLC conference: ‘The emergence of dual-target ADCs is not only a breakthrough in efficacy but also validates the scientific basis of ‘pathway synergistic inhibition’. For 20ins patients, the transition from ‘no drugs available’ to ‘precise selection’ is being written through the intertwining of ADCs and immunotherapy, creating a new chapter in the treatment of EGFR mutations.
Conclusion
The treatment history of EGFR 20ins mutations is an evolutionary tale from ‘despair’ to ‘hope’. When the ‘bullets’ of ADCs hit the target precisely, and the ‘engine’ of immunity is reignited, those mutations once deemed ‘hard-to-treat’ will become the starting point for ‘treatable’. In the future, as more combination strategies are implemented, the survival time of 20ins patients may break through the unit of ‘months’ and move towards a longer ‘years’ era.
(Data as of September 2025, clinical trial information sourced from ASCO, WCLC, and The Lancet Oncology)
(This article is for medical science popularization only; please follow medical advice for specific diagnosis and treatment)