doi:10.1136/jitc-2024-008817Open access Four patients were enrolled at dose level 3, all in cohort A. Patient 11 developed grade 3 immune- related myositis (without any signs of myocarditis) and adrenal insufficiency after six vaccinations and six cycles of ICI. Patient 12 developed grade 3 immune- related nephritis after four vaccinations and five series of ICI. These side effects are well- documented toxicity risks in connection with ICI therapy and thus judged must likely related to this treatment. The myositis and nephritis were managed with steroid therapy and resolved within 4 weeks. In summary, most AEs were grade 1, except for four events (abdominal pain, fatigue, edema, and joint pain), which were reported as grade 2, and two AEs (nephritis and myositis) were registered as grade 3, judged as related to ICI (table 2). Both patients with grade 3 AEs ceased treatment with ICI and EVX- 01- CAF09b as defined per protocol. The most frequent reported AEs were pain at the injection site, fatigue, and nausea. Between the two vaccination routes, a tendency for more side effects was seen after IP injections compared with IM injections.One patient from group 1 died unexpectedly 4 months after the sixth vaccination. It was determined as treatment- unrelated and cancer- unrelated reasons. Majority of patients have CRs to the combined EVX-01 and anti- PD-1 treatment Eight of the 12 patients treated with the combination of anti- PD- 1 and EVX- 01 vaccination achieved objective response: six patients with partial response (PR) and two patients with CR (figure 1B). One patient (patient 11) had a durable response while remaining patients progressed at some point during the trial. At dose level 1, three patients had objective responses comprising one CR with a duration of response (DOR) of 10 months and two PR with DOR of 28 and 5 months. At dose level 2, one patient had PR (60% regression in target lesions) with DOR of 9 months. This patient had been treated with 10 cycles of anti- PD- 1 at the time of inclusion, with SD as the best response, and developed PR 7 months after the first vaccination. The patient devel- oped temporary complete regression in target lesions (100 %) and a stable non- target lesion (online supple- mental figure 1). At dose level 3, all four patients obtained objective responses. Three patients obtained a PR with DOR of 8, 4, and 2 months. Patient 11 has ongoing CR for +16 months. EVX-01 induces vaccine-specific T cell responses in all patients EVX- 01- specific T- cell responses were evaluated on peptide pool restimulation of in vitro stimulated (IVS) PBMCs using both IFN-γ ELISpot (ELISpot) and ICS analyses (figure 3A). To increase the resolution of the analysis, specific T- cell responses were evaluated by indi- vidual neoantigen- peptide stimulation using ELISpot. T- cell reactivity to the vaccine was evaluated at baseline (T1), before EVX- 01- CAF09b vaccine initiation (T2), and after administration of EVX- 01 vaccine (T3=after three IP vaccinations and T4=after three additional IM vacci- nations). Some patients had up to five follow- up samples (FU1–FU5) for analysis of T- cell responses collected approximately at 12- week intervals. Magnitude of T-cell responses to neoantigen peptides correlates with individual dose levels The number of individual neoantigen responses detected by ELISpot before vaccination (T1 and T2), after vaccination (T3 and T4), and in follow- up samples (FU1–FU5) are delineated in table 3. PBMC samples from all 12 patients were analyzed by ELISpot assay, where EVX- 01 prestimulated PBMCs were restimulated with individual EVX- 01 peptides (n=91 neoan- tigen peptides in total). Overall, we observed T- cell responses toward 53 of the 91 analyzed EVX- 01 peptides (58%). Among these, peptide- induced immune responses toward 45 EVX- 01 peptides were exclusively detected after initiation of vaccina- tion. Hence 85% (45/53) of the immunogenic neopeptides have induced a de novo responses. The three dose levels showed similar amounts of total neoantigen responses and de novo responses (table 3).Table 2 Adverse events at dose levels 2 and 3 Dose level 2 (n=3)Dose level 3 (n=4) IP IM IP IM All adverse reactions within 0–14 days Any 12 3 13 12 Grade 2 1 0 2 2 Grade 3 0 0 0 3 Injection site adverse reactions within 0–14 days Pain grade 1 2 0 6 4 Systemic adverse reactions witin 0–14 days Abdominal pain grade 1 1 0 0 0 Abdominal pain grade 2 1 0 0 0 Chils grade 1 0 0 1 0 Cough grade 1 1 0 0 0 Fatigue grade 1 1 1 1 2 Fatigue grade 2 0 0 1 1 Fever grade 1 2 0 0 0 Influenza like symptoms grade 1 0 0 3 0 Headache grade 1 0 0 0 1 Joint pain grade 1 0 0 1 0 Joint pain grade 2 0 0 1 0 Nausea grade 1 3 1 0 0 Vomiting grade 1 2 1 1 0 Edema grade 2 0 0 0 1 Myositis grade 3 0 0 0 1 Adrenal insufficiency grade 3 0 0 0 1 Papilledema grade 1 0 0 1 0 Nefritis grade 3 0 0 0 1 IM, intramuscular; IP , intraperitoneal. 9 Mørk SK, et al.