Table 1.

Previous experience in lung cancer immunotherapy

CYTOKINES
MODALITY	REFERENCE	OUTCOMES	CAVEATS
IL-2	Rosenberg 1994 Rosenberg 1998 Dillman 1993 Fyfe 1996 Klapper 2008	14-20% RR in patients in melanoma and RCC patients. 5-9% CRR, majority of them long-lasting. FDA-approved for RCC in 1992. FDA-approved for melanoma in 1998.	Limited experience in lung cancer patients (3/7 responders). Severe, commonly transient, toxicity due to increased vascular permeability. Need for intensive monitoring and vasoactive drugs.
IL-2 combinations	Lissoni 1994	Phase 2 trial comparing low-dose IL-2 + melatonin vs. CDDP + VP-16 in NSCLC: similar RR, PFS and OS in the chemotherapy-free group.
	Ridolfi 2011	Phase 3 trial comparing CT +/− low dose IL-2 in NSCLC: no relevant differences in clinical outcomes.	Higher G4 toxicity in the IL-2 containing arm.
IFNα	Prior 1997 Ruotsalainen 1999 Tummarello 1997	IFNα-2b FDA-approved in 1995 for adjuvant treatment of high-risk resected melanoma. Three randomized placebo- controlled phase 3 trials in SCLC: CT +/− IFNα. Improved RR and OS have been reported in some (Prior, Tumarello), while others failed to show influence on survival (Ruotsalainen).	Pyrexia and grade 3-4 hematologic AEs were more frequent in the IFNα arms.
INNATE IMMUNITY AND ADJUVANTS
MODALITY	REFERENCE	OUTCOMES	CAVEATS
TLR-9 agonist: PF-3512676	Manegold 2008	Randomized placebo controlled phase 2 trial for advanced CT-naïve NSCLC patients: CT +/− PF-3512676. Improved response rate: 19 vs. 11%. Trend towards prolonged OS.	Grade ≥3 anemia, thrombocytopenia and neutropenia more commonly reported in the PF-3512676 arm.
Bacterial adjuvants Killed Mycobacterium vaccae	O’Brien 2004	Randomized phase 3 trial in advanced NSCLC: CT +/− intradermal vaccination. No difference in OS.	No relevant safety concerns.
Bacterial adjuvants Killed Mycobacterium indicus pranii	Belani 2017	Randomized placebo-controlled trial for treatment naïve advanced NSCLC: CT +/− vaccine. No OS differences in the ITT population. Subgroup analyses suggested SCC patients derived a significant OS benefit.	No differences in systemic AEs.
DC maturation agents Talactoferrin	Ramalingam 2013	Placebo-controled phase 3 trial.	No differences in DCR, PFS or OS.
VACCINES
Peptide-based antigen delivery
MODALITY	REFERENCE	OUTCOMES	CAVEATS
EGF conjugated with N. meningitides P64K peptide (CY 200 mg/m2 before first vaccine dose)	Neninger-Vinageras 2008	Randomized phase 2 trial of maintenance therapy after first-line CT for advanced NSCLC. Statistically non-significant trend towards prolonged OS.	No grade 3-4 AEs observed.
	Xing 2018	Phase 1, single arm vaccination trial for patients with advanced NSCLC who remain PD-free after first-line CT. No objective responses reported.	No DLTs in the four dose levels explored.
MUC1 (EMA)-derived peptide in a liposomal preparation (CY 300 mg/m2 before first vaccine dose)	Butts 2005 Butts 2011 Butts 2014 Katakami 2017	Expressed in most ADCs. Randomized phase 2b trial of maintenance therapy after first-line CT for advanced NSCLC. Non-significant trend towards prolonged OS. OS benefit is greater in patients with locally advanced disease (subgroup analysis) (Butts, 2005 and 2011). Randomized phase 3 placebo-controlled maintenance therapy after CRT for stage III NSCLC. Non-significant trend toward improved OS. Greater benefit in patients who had received concurrent vs. sequential CRT (subgroup analysis) (Butts 2014). This was not confirmed in a phase 2 trial conducted in Japanese patients with stage III NSCLC (Katakami).	No relevant safety concerns. Slightly higher incidence of CNS metastases in the vaccination arm in the phase 3 trial.
GV-1001: telomerase reverse transcriptase (hTERT) peptide + GM-CSF 75 μg	Brunsvig 2011	Phase 1 trial in advanced NSCLC patients. Significantly prolonged OS in patients that had an in vitro T-cell response to the peptide. Phase 2 trial of vaccination after CRT for stage III NSCLC. Trend toward improved PFS in patients that had an in vitro T-cell response to the peptide.	No serious TRAEs.
IDO-peptide	Kjeldsen 2018	Phase 1 single-arm trial for advanced NSCLC patients who remained PD-free after CT. 2/15 objective responses. 6-year OS: 3/15.	No grade 3-4 AEs in long-term responders (2/15).
Peptide vaccination according to baseline IgG titers against five antigens	Sakamoto 2017	Phase 2 trial in advanced SCLC patients. IgG responses to non-vaccinated peptides were associated with OS.	Grade-3 AEs were limited to the skin.
Racotumomab: anti-NeuGcGM3 ganglioside anti-idiotype antibody	Alfonso 2014	Phase 2/3 placebo-controlled maintenance therapy for advanced NSCLC patients after first-line therapy. Statistically significant prolongation of PFS and OS. Neutralizing and cytotoxic IgM seronconversion was associated with survival.	No relevant safety concerns.
Peptide-based neo-epitope vaccination	Keskin 2018	Induction of neo-epitope specific T cell responses in glioblastoma patients.	Limited experience in lung cancer
mRNA-based antigen delivery
MODALITY	REFERENCE	OUTCOMES	CAVEATS
mRNA encoding for five tumor-associated antigens: NY-ESO-1, MAGE-C1, MAGE-C2, surviving and 5T4	Sebastian 2019	Phase 1/2a single-arm trial for advanced NSCLC patients who remained PD-free after first-line treatment. No objective responses. Median PFS: 5.0 m. Median OS: 10.8 m.	No grade≥4 TRAEs.
RNA-based poly-neo-epitope vaccination	Sahin 2017	Induction of neo-epitope specific T cell responses in melanoma patients. 2/5 stage-IV melanoma responders.	Limited experience in lung cancer.
Cell-based antigen delivery
MODALITY	REFERENCE	OUTCOMES	CAVEATS
Autologous GM-CSF-producing irradiated tumor cells	Davies 2007	Phase II single-arm trial in patients with advanced BAC. No objective responses.	Patients have to undergo surgery to obtain tumor tissue. Complex manufacturing process that led to low accrual.
Allogeneic intradermal tumor-cell lines transfected with TGF-β2 antisense vector.	Giaccone 2015	Phase 3 randomized placebo-controlled maintenance therapy after front-line therapy for advanced NSCLC. No OS benefit in the ITT analysis. Positive OS prolongation in patients who received CRT prior to randomization (pre-specified subgroup analysis).	No serious safety concerns.
Tergenpumatucel-L: allogeneic intradermal tumor-cell lines modified to express α1,3-Gal	Morris 2013	Phase 2 single-arm trial for previously-treated advanced NSCLC. 8/28 SD lasting ≥16 weeks. Median OS: 11.3 months. 9/16 responses to subsequent CT, suggesting a chemo-sensitization effect.	No concerning safety issues.
GM-CSF- and CD40L-producing bystander cell line + two allogeneic tumor cell lines +/− CCL21-producing adenoviral vector	Gray 2018	Phase 1/2 trial for previously treated ADC patients. No PFS or OS differences between treatment groups.	No grade ≥3 toxicity reported.
Viral vector-based antigen delivery
MODALITY	REFERENCE	OUTCOMES	CAVEATS
Lentivirus-NY-ESO-1	Somaiah 2019	Anti–NY-ESO-1-specific CD4 and/or CD8 T cells induced in 57% of patients. DCR: 56% in a cohort composed mainly of patients with sarcomas, melanoma and ovarian cancer. Only 1/38 responder.	Limited clinical evidence in lung cancer (n=1). There might had been central tolerance to eliminate non-mutant protein-reactive T cells.
TG4010: modified vaccinia Ankara that codes for MUC1 and IL-2	Quoix 2016	Phase 2b placebo-controlled trial for MUC1-expressing (≥50% tumor-cells by IHC): CT +/− subcutaneous TG4010. Improved RR (40 vs. 29%) and PFS, but not OS in the ITT population. Subgroup analyses suggested that non-squamous tumors and low blood CD16+CD56+CD69+ cell counts derived the greatest benefit.	No relevant safety concerns.
APC delivery
MODALITY	REFERENCE	OUTCOMES	CAVEATS
Ad.p53-DC: TP53-transfected dendritic cells +/− ATRA	Chiappori 2019	Phase 2 trial of Ad.p53-DC +/− ATRA or placebo in ED-SCLC who remained PD-free after first-line CT, followed by paclitaxel at PD. ORR to paclitaxel was higher in Ad.p53-DC+ATRA compared to Ad.p53-DC monotherapy and placebo arms: 24, 17 and 15% respectively. No significant OS differences, although numerically higher in the placebo arm.	No grade-4 toxicity reported.
MONOCLONAL ANTIBOIDES AND BiTEs
MODALITY	REFERENCE	OUTCOMES	CAVEATS
ADCC - Cetuximab	Lynch 2010 Pirker 2009 Rosell 2008	Predictive early-onset acneiform rash may be immune mediated.	Modest OS improvement over standard CT alone. No regulatory agency approval.
BITEs CEA-CD3	Ordoñez 2006 Tabernero 2017	Positive in a significant proportion of lung ADC and non-keratinizing SCC. 5% RR in CRC (higher if combined with Atezolizumab: 20%).	Limited experience in lung cancer patients. Significant systemic and on-target (off and on-tumor) toxicity.
BITEs EpCAM-CD3	Kebenko 2018	Expressed in ADC and SCLC. Nine lung cancer patients included.	Limited activity. Limiting on-target off-tumor toxicity (diarrhea, liver enzimes): 95% of patients with grade≥3 AEs.
BITEs DLL3-CD3	Tanaka 2018 Rudin 2017 Smit 2019 Hipp 2020	32-67% of SCLC with ≥50% tumor-cell expression. Well tolerated in cynomolgus monkeys.	Only preclinical evidence of activity. Ongoing clinical trials.
ACT
MODALITY	REFERENCE	OUTCOMES	CAVEATS
Anti-NY-ESO-1-TCR-transduced T-cells	Jungbluth 2001 Robbins 2015	Expressed (IHC) in 25% of NSCLC. No relevant off-tumor toxicity (1 death due to preparative CT-induced neutropenia).	Limited clinical evidence in tumors other than melanoma and synovial sarcoma.
Anti-MAGE TCR-transduced TILs	Kerkar 2016 Morgan 2013 Lu 2017	Expressed in 24-34% lung tumors. 5/9 PR in melanoma and synovial sarcoma (Morgan). 4/17 RR in patients with a variety of solid tumors (Lu).	HLA-restricted. On-target off-tumor neurologic toxicity, higher for MHC-I restricted TCRs. Limited evidence in lung cancer patients.
PBMC-derived ex vivo stimulated cells	Wu 2008	CT +/− ACT in advanced NSCLC patients. Statistically significant PFS and OS prolongation.	No relevant safety issues reported.
EGFR-directed CAR T-cells	Feng 2016	Phase-1 single-arm trial for relapsed/refractory NSCLC patients with IHC EGFR expression ≥50%. RR: 2/11, short lasting responses.	A single grade-3 AE was described: lipase elevation.

ACT: adoptive cell therapy; ADC: adenocarcinoma; AE(s): adverse event(s); ADCC: antibody-dependent cellular cytotoxicity; APC: antigen-presenting cell; ATRA: all-trans retinoic acid; BAC: bronchoalveolar carcinoma (obsolete term); BiTE: bi-specific T-cell engager; CDDP: Cisplatin; CNS: central nervous system; CRC; colorectal cancer; CRR: complete response rate; CRT: chemo-radiotherapy; CT: chemotherapy; DCR: disease control rate; DLT: dose limiting toxicity; ED: extensive-disease; FDA: Food and Drug Administration; G: adverse-event grade; IDO: indoleamine 2,3-dioxygenase; IHC: immunohistochemistry; ITT: intention-to-treat; NSCLC: non-small cell lung cancer; OS: overall survival; PD: progressive disease; PFS: progression-free survival; PR: partial response; RCC: renal cell carcinoma; RR: response rate; SCC: squamous-cell carcinoma; SCLC: small cell lung cancer; SD: stable disease; TLR: toll-like receptor; TRAE: treatment-related adverse event; VP-16: etoposide;