Background Ovarian cancer is the most lethal gynaecological malignancy, accounting for approximately 185,000 deaths worldwide in 2018. The majority of patients will experience recurrence of disease. Therefore, there is an urgent need for the development of further therapies to improve patient survival. Tumour infiltrating lymphocyte (TIL) therapy has shown clear efficacy in immunogenic cancers, and TIL can be readily expanded ex vivo from samples of high grade serous ovarian cancer (HGSOC). Key indicators of effective TIL products for infusion are high TIL yield and functionality against autologous tumour. Blockade of checkpoint proteins is effective in increasing TIL yield and functional response from ovarian cancer TIL cultures. However, it is unknown whether blockade of other key checkpoints, including programmed death ligand-1 (PD-1), T cell immunoglobulin mucin-3 (TIM-3) and lymphocyte activation gene-3 (LAG-3) increase TIL yield in ex vivo cultures from HGSOC samples.

Materials and Methods TIL cultures were generated from surgically resected HGSOC tumour samples and were incubated with CD3/CD28 Dynabeads. 3000IU/mL recombinant interleukin-2 (IL-2) was added on alternate days for 7 days before beads were removed. 1000IU/mL IL-2 was added on alternate days for a further 12 days of culture. In cohort 1, 10µg/mL αPD-1, αTIM-3 or αLAG-3 antibodies were added at initiation of TIL cultures only. In cohort 2, 10µg/mL αPD-1, αTIM-3 or αLAG-3 antibodies were added on alternate days until Day 19. Interferon gamma (IFN-γ) release in response to TIL co-culture with autologous tumour cultures was measured with a human IFN-γ ELISA kit. Data are presented as mean±SEM.

Results Addition of checkpoint inhibitors at the initiation of HGSOC TIL culture in cohort 1 increased TIL expansion above untreated control in αPD-1 (1.20±0.04 fold, P<0.01, n=9) and αLAG-3 (1.31±0.08 fold, P<0.001, n=9) but not αTIM-3 treated cultures. However, intermittent dosing of HGSOC cultures in cohort 2 with either αPD-1, αTIM-3 or αLAG-3 antibodies did not increase TIL expansion above untreated cultures. In cohort 1, IFN-γ secretion was increased above untreated control in at least one culture treated with a checkpoint inhibitor in 5/7 patients. However, there was no overall fold change in IFN-γ secretion in either αPD-1, αTIM-3 or αLAG-3 treated cultures.

Conclusions This data suggests that initial blockade of checkpoint proteins is effective in increasing the ex vivo expansion of TIL from HGSOC tumours, thus providing a method of improving the efficacy of TIL products in ovarian cancer patients.

Funding GO was funded through a CRUK Manchester Centre Clinical Fellowship. PJ was in receipt of a bursary from the Emma Gyles Bursary Fund. The project was funded by TESARO Inc.

Disclosure Information C.A. Waddell: None. M.J. Price: None. P. Johnson: None. R.J. Edmondson: None. G.L. Owens None.