9 months) ( 69). All of these results suggest immunotherapy as an important therapeutic approach in NSCLC patients and thus our study will consider previous checkpoint inhibitor therapy as a stratification criterion for randomization. New results have been published and address the possible benefit of us ing immune checkpoint inhibitor s in 1st line therapy of advanced NSCLC. These results are conflicting with very positive results for anti PD -1 therapy with pembrolizumab in patients with PD -L1 expression over 50% of tumor cells ( 66) but not with anti PD -1 therapy with nivolumab in patients included whatever was the level of PD -L1 expression ( 28). Yet, various combination therapies may be beneficial with reports by Hellmann et al ( 35) or Langer et al ( 45). Thus, it has been advised by the Steering Committee of our study during its December 13th 2015 session that there should be an amendment to the current protocol to allow for inclusion of patients treated with checkpoint inhibitors alone or in combination as 1st line therapy and that patient should anyhow be offered also platinum -based chemotherapy (1st or 2nd line) before entering the trial. This led to version 3.0 of the prot ocol. Numerous studies evaluating ICIs as stand -alone and in combination are ongoing in early stage . In 2017, durvalumab as maintenance treatment for one year after radical treatment with concurrent chemo -radiotherapy in locally advanced unresectable NSCLC show ed an improvement in median time to death or distant metastasis of 23.2 months in durvalumab arm vs. 14.6 months in placebo arm ( 1). In 2019 , immunotherap ies play an important role in the treatment of NSCLC (62). Since 2015, four anti PD -(L)1 monoclonal antibodies ( nivolumab, pembrolizumab , atezolizumab and durvalumab ), alone and in combination with various compounds (i.e. ipilimumab, or OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 30 of 101 02 February 2022 chemotherapy ± bevacizumab), have consistently demonstrated a superiority of overall survival in first and second -line treatment in advanced NSCLC and in locally advanced unresectable NSCLC . Overall, in advanced NSCLC, a meaningful improvement of long-term OS rate at 3 and 5 years of 25% is maintained with ICIs ( 62). This major improvement in therapy, albeit with limited response rate ( 10, 60) when ICI are used as monotherapy, led us to consider that, where available, checkpoint inhibition would be offered before moving to investigational th erapy and thus that the current Phase II /III target should include 2nd or 3rd line therapy in patients with no therapeutic alternative after failure of platinum and immune checkpoint inhibition. In 2018, data of durvalumab + tremelimumab were reported in 78 immunotherapy -pretreated advanced NSCLC patients ( 27). 94% of patients received ≥ 2 lines of prior therapy including PD -1 or PD -L1 inh ibitors. 40 (51%) patients “relapsed” after ICI (defined as responders, then progression; prior median time to progression of 7 mo) and 38 (49%) were “refractory” to previous ICI (defined as no response; prior median time to progression of 2.6 mo). The com bination durvalumab + tremelimumab was manageable . Severe (Grade 3 and 4) related AEs occurr ed in 28% of patients, with diarrhea (6%) being most common. 5 patients (6%) discontinued due to a treatment -related AE. No treatment -related deaths were observed. Objective response rate was reported in 4 ( 5.1% ) patients [2(5%) patients in relapsed group, 2(5.3%) patients in refractory group]. Median progression -free survival (PFS) was 1.8 mo (95% CI; 1.6 -2.5) [2.5 mo (95% CI; 1.6 -3.5) in relapsed group, 1.7 mo (95% CI; 1.6 - 1.7) in refractory group]. Median overall survival (OS) was 8.4 mo (95% CI; 6.2 -10.4) [8.5 mo (95% CI; 4.0 -14.3) in relapsed group, 8.3 mo (95% CI; 6.0 -10.4) in refractory group. OS rate at 12 months was 34.1 % (37.5 % in relapsed group, 3 0.1% in refractory group). These l imited data comfort our current statistical assumption that an OS -rate at 12 months of 40% is a relevant efficacy target in this population. However, the continuation of the study in Step 2 which plans to demonstrate a better survival of OSE2101 over the control group (HR 0.7), will be discussed at the end of Step 1 between the steering committee (SC) and the Sponsor based on the recommendations of the independent data monitoring committee (IDMC) . Since the start of the study in 2015, there have been major forward advances in the management of NSCLC. The decision of continuing the study in Step 2 (Phase 3) will consider the expected benefit of OSE2101 as well the relevance of the specific design of the Phase 3 in regards of the state of the art in the management of advanced NSCLC k nown at time of the analysis (see Section 6.7). Moreover, different vaccines have been designed for specific peptide epitopes in NSCLC ( 79). In the adjuvant setting, the Phase III MAGRIT trial did not report improvement in disease free survival with the recMAGE -A3 + AS15 cancer immunotherapeutic (MAGE -A3 CI) as adjuvant therapy compared with placebo in patients with stage IB -IIIA c ompletely resected MAGE -A3- positive NSCLC, even in the population who did not receive adjuvant chemotherapy ( 78). In locally advanced disease, the Phase III START trial, randomly assigned 1,513 patients with unresectable stage IIIB NSCLC following definitive chemoradiation to L -BLP25 (liposomal vaccine) with best supportive care (BSC) or placebo plus BSC. The trial failed to meet its primary endpoint of improved OS with L -BLP25 (25.6 vs. 22.3 months for placebo; P=0.123) OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 31 of 101 02 February 2022 (13). In advanced disease, different vaccines have been tested such as Belagenpumatucel -L (54), EGF vaccine (32), TG4010 vaccine (TIME trial) ( 63) or IDO vaccine ( 40). However, heterogeneity of tumor -associated antigen (TAA) expression, the potential for tumor associated antigen (TAA) loss, and variability of the human T -cell repertoire suggest that effective cancer T-specific immunotherapies require ind uction of a wide breadth of cytotoxic T lymphocytes (CTL) specificities. This can best be achieved with T -specific immunotherapies targeting multiple TAAs. 1.2 OSE2101 The OSE2101 T -specific immunotherapy was designed to induce CTLs against five TAAs frequent ly overexpressed in NSCLC (i.e. carcinoembryonic antigen [CEA], p53, HER -2/neu, and melanoma antigens MAGE2 and 3). These TAAs have been used alone in previous studies involving NSCLC patients. OSE2101 is composed of 10 synthetic peptides from these TAAs, nine of the peptides representing CTL epitopes and one pan -DR epitope. Each CTL epitope is restricted by HLA -A2.1 and at least one other member of the HLA -A2 superfamily of major histocompatibility complex class I molecules. HLA -A2 phenotype is expressed b y approximately 45% of the general population as well as cancer patients. These epitopes being HLA -A2 restricted means that they can bind only HLA -A2 molecules to be presented to the T -lymphocyte and thus, can only be effective in patients having HLA -A2 ph enotype. The pan -DR epitope (PADRE) is a rationally designed helper T -lymphocyte (HTL) epitope included to augment the magnitude and duration of CTL responses ( 5). The innovation is to associate epitopes designed and modified chemically (analogs), of different tumor antigens in the same combination. Some of these analogs will increase the HLA -A2 bindi ng and others will increase the T cell receptor binding. It was previously demonstrated that all of the epitopes selected were immunogenic. The utility of the analog peptides was further documented, as the CTLs generated were capable of recognizing wild-type epitopes expressed on tumor cell lines. Moreover, others have demonstrated measurable recall or post -vaccination CTL responses against most of the nine CTL epitopes (including the wild -type versions of analogs in the current product). The immunogenicit y of OSE2101 after in vivo immunization was also demonstrated in HLA -A2.1/Kb transgenic mice, which express the human HLA -A2.1 molecule (refer to investigator brochure) OSE2101 clinical trials In two phase I trials in stage IIB -IIIA NSCLC (NCT00054899) a nd stage III colon cancer (NCT00054912) patients, subcutaneous OSE2101 was administered at 5 mg peptide/dose at 3 - week schedule for a total of 6 doses. The objectives were to evaluate the safety and immunogenicity of OSE2101 measured by IFN -γ ELISPOT assay s. A total of 16 out of 24 enrolled patients completed six injections over 18 weeks (6 out of 10 NSCLC patients, and 10 out of 14 colon cancer patients). The most common adverse event in the 24 patients who received at least one dose of the OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 32 of 101 02 February 2022 OSE2101 was reaction at the site of injection (erythema, pain, granuloma, and induration). Other side effects were: fatigue, rigors, nausea, vomiting, arthralgia, myalgi a, pain in the extremities and dyspnea. Only 1 out of 24 patients reported an immune -related adverse event with a cytokine release reaction (fever, chills, chest pain, nausea and apnea) that was resolved within 24 hours of hospitalization . A strong CTL re sponse was observed in the majority of patients tested. Immune response was defined in the protocol as one (or more) epitope -specific response greater than two standard deviations above background values as assessed by the ELISPOT assay. 15 out of 16 pati ents receiving 6 injections were responding (93%) indicating that the T -specific immunotherapy was immunogenic and effective at inducing strong and broad CTL responses in a high frequency of patients (only one patient out of the 16 failed to respond to the T-specific immunotherapy, the expression of a less cross -reactive subtype in the HLA -A2 supertype family, HLA -A*0207, most likely accounted for the lack of immunogenicity in this patient). With respect to breadth of responses, eight of the 15 patients gen erated CTL responses to over half (five or more) of the epitopes in OSE2101 and, on average, each patient induced CTL responses to approximately four epitopes. In NSCLC patients, HLA -A2 is expressed as in the general population ( 22, 74) and is thought to be between 40 and 50%. Interestingly, HLA -A2 positivity appears as being an independent negative prognostic factor in cancers ( 48) and also in NSCLC: the role of HLA -A2 measured by blood sampling has been established by different and independent teams in large series of patients. Serological HLA -A2 expression appears as an independent risk factor of lymph node involvement and distant metastasis ( 12, 51, 47). However, a more recent analysis has shown that the HLA -A2 status was not identified as a progno stic factor in a large advanced NSCLC population treated with platinum -based chemotherapy ( 84). A Phase II , open -label, multicenter, single dose -group, multiple administration study of OSE2101 in patients with HLA -A2 positive advanced NSCLC was performed (NCT00104780) (4, 53, 54). The study was designed to evaluate the safety, efficacy ( response and survival), and immunogenicity of OSE2101 in patients with advanced NSCLC who were HLA -A2 positive. The T -specific immunotherapy was administered subcutaneously at a dose of 5 mg every 3 weeks for the first 15 weeks, then every 2 months through year 1, then quarterly through year 2, for a total of 13 doses. Patients were to be followed at three months after the last injection. Survival status was then to be ascertained every three months through year three then annually until year five. Tumor assessment was performed at baseline with reassessment at weeks 9 and 18 and at months 6, 9, and 12. Leukapheresis was performed before vaccination (at screening) and at weeks 9 and 18 to obtain sufficient cells to conduct the immunogenicity assays. Hematol ogy, electrolytes, liver, other organ functions, urinalysis, and antinuclear antibody titer were assessed. Toxicity was monitored and graded according to the National Cancer Institute Common Toxicity Criteria. All patients signed the protocol -specific loca l institutional review board approved informed consent form. Response Evaluation Criteria in Solid Tumors were used to evaluate response. OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 33 of 101 02 February 2022 Eligible patients for this study were 18 years or older with histologic confirmation of stage IIIB or IV or recurrent NSCLC. Patients had to have an Eastern Cooperative Oncology Group performance status of 0 or 1, an absolute granulocyte count ≥ 1,500/µL, platelet count ≥100,000/µL, hemoglobin ≥ 10 g/dL, total bilirubin ≤ 2 mg/dL, AST and ALT 2 ≤ 5 times the upper limit o f normal, and serum creatinine ≤ 2 times the upper limit of normal. Patients with brain metastases were eligible if the disease was clinically stable for at least 2 months before study entry. A second group of patients who were HLA -A2 negative when screene d for the study were identified to use as an observational comparator group. The patients were assessed for survival via access to the social security death index. Overall survival was estimated using the Kaplan -Meier method. Progression -free survival was to be determined from time of patient registration to date of progression, death or last assessment of tumor response. To measure CTL responses, 2*106 peripheral -blood mononuclear cells (PBMCs)/well (three to four wells per epitope) were stimulated in v itro with each peptide (10 µg/mL). Ten U/mL of rIL - 2 was added after 24 hours. After 10 days of culture, the in vitro –expanded PBMCs were tested for epitope -specific (T -specific immunotherapy epitope and wild -type epitope of an analog) CTL responses, measu red by an 18 -hour interferon gamma ELISPOT assay. Immune response relationship to survival was done by comparing the number of epitopes with measurable enzyme -linked immunosorbent spot assay (ELISPOT) responses in relation to survival using the log -rank st atistic. Results: A total of 135 patients were enrolled; 64 patients were positive for HLA -A2 and 72 patients were HLA -A2 negative with the information provided only for survival. The 64 HLA -A2 positive patients were treated with one or more dose(s) of OSE2101 and represent the ITT population and the safety population. Of these 64 treated patients, 31 (48%) completed the treatment phase and 11 (36%) subsequently completed the follow -up phase. The majority of the early withdrawals from the treatment phase (27%, 17/64 patients) as well as from the continuation and follow -up phases (19%, 12/64) were due to disease progression and/or decline in health status. Eight patients (13%) completed all phases of the study. Four patients (6%) withdrew from the study due to an AE. The characteristics of the 64 HLA -A2 positive patients were as follows: • Median age 64 (26 -87) • Male 55%; Female 45% • Caucasian 83%, African American 9%, Asian 8% The majority of patients (43/64, 67%) had Stage IV NSCLC at inclusion. The median number of days since first diagnosis was 416 (range of 74 to 1921 days). Prior treatment lines for OSE2101 treated patients were: • one previous line in 31% of patients; OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 34 of 101 02 February 2022 • two previ ous lines: 28% • 3 or more previous lines (up to 6 lines): 37.5% 92% of the treated population had previously received a platinum -based chemotherapy and 34% a TKI (gefinitib or erlotinib). 6 patients (9.4 %) had received previous radiotherapy for brain meta stasis. 18 patients were considered as progressive disease at entry, representing 28% of this treated OSE2101 population. The HLA -A2-negative non -treated population demographics were similar to the HLA -A2 positive treated population: 72 patients: age 65 ( 33- 91); male 37 (51%), female 35 (49%); Caucasian 57 (79%). One out of the 72 patients was lost of follow -up. Overall survival Median survival for HLA -A2-positive treated patients was 17.3 months. In the HLA -A2- negative non -treated group, the median survival was 12.0 months. One-year survival in OSE2101 treated patients was 60%, compared to 49% in the HLA -A2- negative group ( 53). The two -year and three -year survival estimates for OSE2101 treated patients were 39% and 27%. Clinical evaluation on the 64 HLA -A2+ treated patien ts (ITT population) One patient had a complete response and one a partial response. Stable disease of 3 months or greater was observed in 54 (86%) additional patients, translating into a clinical benefit in 89% of patients. Seventeen (27%) patients conti nued treatment for one year and demonstrated no evidence of progressive disease. Fourteen (22%) patients completed two years of dosing and remained without evidence of progressive disease. Progression free survival was 285 days (median time to progressio n) Immune Response Immune response was assessed in 33 treated patients. All 9 epitopes were immunogenic in at least 1 patient. Five epitopes showed strong responses that cross -reacted with wild type (WT) peptide. In analyzing the strongest 5 epitopes, 91 % of patients demonstrated CTL epitope response to at least one antigen. Eighty -five percent demonstrated responses to 2 or more, 64% to 3 or more, 39% to 4 or more, and 18% to 5 or more. Correlation with survival was demonstrated in patients generating immune response. Longer survival was correlated with a higher number of positive epitopes (response was assessed by ELISPOT for the 5 strongest, CEA24, CEA605, HER2.369, MAGE2.157 and MAGE3.112). The Log Rank test showed decreased survival among those wit h a low immune response level compared to those with a medium or high immune response level (p<0.001). • Low: 0 -1-epitopes: 406 ± 58 days of survival (n=5; 95% CI for mean 292 -520) • Medium: 2 to 3 -epitopes: 778 ± 72 days of survival (n=15; 95% CI for mean 637 -919) • High: 4 to 5 -epitopes: 875 ± 67 days of survival (n=13; 95% CI for mean 743 - 1007) . OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 35 of 101 02 February 2022 Interferon -γ producing helper T cells against PADRE were detected in 18 of 33 (55%) patients tested in a direct ELISA assay. The durability of the CTL induction was also demonstrated by responses to 4 of 5 epitopes in 3 of 4 patients tested at 12 months. In conclusion , the OS difference observed is 17.3 months of median OS in the OSE2101 treated group versus 12 months in the observational HLA -A2 negative group. The OS rate at one year was 59% in the treated HLA -A2 positive group versus 49% in the observational HLA -A2 negative group. The HLA -A2 observational group represents a “worst case” contro l group given that the prognosis is superior to the treated HLA -A2 positive group. The data collected from the observational group is adequate to allow a meaningful comparison of one -year OS to the OSE2101 treated group. The median survival achieved is im portant for the OSE2101 Phase II highly pretreated population (65.5% received more than 2 lines, 92% received previous platinum -based chemotherapy). The median survival for the three registered treatments (docetaxel, pemetrexed and erlotinib) after first line therapy is approximately 8 months and the one-year survival rate is 33%. In the OSE2101 Phase II , longer survival was significantly correlated with a higher number of positive e pitopes. Furthermore, the long –term survival achieved at 4 years for the treated patients was complemented by a favorable safety profile. These OSE2101 clinical data support a recommendation that OSE2101 move forward to a Phase III trial in HLA -A2 positive patients with advanced NSCLC who have previously failed first or subseq uent line of therapy. Additional information on OSE2101 is available in the investigator’s brochure. 1.3 Design considerations Target indication : Based on the Phase II OSE2101 results and ESMO and ASCO treatment guidelines ( 2, 3, 65, 62), the targeted population in a Phase III trial should be patients with stage III unsu itable for radiotherapy or metastatic stage IV NSCLC in second - or third -line treatment. Since 2015, immunotherap ies (PD-(L)1 ± CTL -A4 inhibitors) play an important role in the treatment of NSCLC with a meaningful improvement of long -term OS rate at 3 and 5 years of 25% in advanced disease. More recently in 2017, durvalumab as maintenance treatment for one year after radical treatment with concurrent chemo -radiotherapy in locally advanced unresectable NSCLC shown an improvement in median time to death or distant metastasis of 23.2 months in durvalumab arm vs. 14.6 months in placebo arm (1). This major improvement in therapy, albeit with limited response rate ( 10, 60) when used as monotherapy , led us to consider that, where available, checkpoint inhibition would be offered before moving to investigational therapy and thus that the Phase III target should include 2nd or 3rd line therapy in patients with no therapeutic alternative after failure of platinum and immune checkpoint inhibition. Therapy : Reference therapy should be available and approved alike in the US and Europe as the trial extent needed to reach these 2 regions and thus only docetaxel and pemetrexed meet this OSE2101 Protocol OSE2101C301 Confidential Version n°6.0 Page 37 of 101 02 February 2022 Randomization : This Phase III study needs to be randomized but cannot be blinded as study treatment and reference therapies have different routes of administration, need concomitant therapy that would not be allowed for OSE2101 (steroids) and safety profile would easily help to recogn ize treatment allocated. Thus, the study will be open -labelled (not blind).