Background: Human epidermal growth factor receptor 2 (HER2) exon 20 insertions and mutations are oncogenic drivers found in 1-2% of NSCLC. However, there are no approved therapies for these patients. Many studies suggest that the use of HER2 inhibitors developed for breast cancer patients might be of interest in this setting. The aim of this trial was to prospectively evaluate the interest of a combination of two antibodies against HER2 (trastuzumab and pertuzumab) with docetaxel. Methods: IFCT-1703 R2D2 trial is a multicenter, non-randomized phase 2 study with a two-stage design, a power of 90% and an alpha risk at 5% (one-sided). HER2 mutational status was assessed locally in certified molecular genetic centers. Main other inclusion criteria were advanced NSCLC, progression after ≥ 1 platinum-based chemotherapy, asymptomatic brain metastases, left ventricular ejection fraction (LVEF) ≥ 50%, and PS 0-2. Patients were treated every 3 weeks with pertuzumab at a loading dose of 840 mg, and 420 mg thereafter; plus trastuzumab at a loading dose of 8 mg/kg and 6 mg/kg thereafter; and docetaxel at 75 mg/m². Treatment was given until toxicity or disease progression. The primary outcome was overall response rate (ORR). Other endpoints included duration of response, progression-free survival and safety. NCT number: NCT03845270. Results: From May 2019 to October 2020, 45 patients were enrolled in 17 centers and received study treatment. Median age was 64.5 years (range 31–84), 72% females, 35% smokers, 100% non-squamous histology and 15% with ECOG PS 2. 31.1% patients had brain metastases. PD-L1 was expressed ≥ 1% and ≥ 50% in 36% and 7% of the patients, respectively. No other oncogene driver was found associated with HER2 exon 20 mutation. With a median follow-up of 12 months, 44 (98%) patients were evaluable for the primary endpoint. Overall response rate was 29% (n = 13), stable disease 56% (n = 26). Median PFS was 6.8 months (95% CI[4.0-8.5]). Median duration of treatment in patients with confirmed response (n = 13) was 10 months (95% CI[2.7-14.9]). At the time of data cut-off, 15 patients (33%) were still under treatment. Grade 3/4 treatment-related adverse events (AEs) were observed in 64% of patients. No patient experienced treatment discontinuation because of toxicity. One sudden death was possibly related to treatment. Most frequent grade ≥ 3 AEs were neutropenia (33%), diarrhea (13%) and anaemia (9%). Grade 1/2 dyspnea was observed in 3 (6.7%) patients. No ILD were reported. Variation LVEF was -1.72% on average (min: -18 %; max: 10 %). Conclusions: The triplet trastuzumab, pertuzumab and docetaxel is feasible and active in HER2 pretreated advanced NSCLC. These results confirm the activity of HER2 antibodies-based strategy which should be considered in these patients. Clinical trial information: NCT03845270