Programmed death-1 ( PD-1 ) is a co-inhibitory receptor expressed on activated T cells which regulates antitumor immunity.
Nivolumab ( Opdivo ) is a fully-humanized IgG4 that blocks the engagement of PD-1 by PD-1 ligands.
Researchers previously showed Nivolumab can mediate tumor regression in a substantial proportion of patients with ovarian cancer in phase II trial ( ASCO 2014 ), but the potential of durable anti-tumor response by Nivolumab for these patients was unknown.
Patients with Platinum-resistant ovarian cancer ( n=20 ) enrolled from 2011 to 2014 were treated with Nivolumab ( 1mg/kg, n=10; 3mg/kg, n=10, each ) intravenously every two weeks up to one year were followed how long anti-tumor response continued.
Among 20 patients in whom response could be evaluated, researchers followed two patients with complete response in 3 mg/kg cohort and one patient with partial response of 1 mg/kg cohort.
At the time of data cut off, a partial responder had responses for 5 months, and two complete responders survived without disease progression for 17 and 14 months, each.
The duration of response of these patients after treatment discontinuation was 6 months and 3 months, each.
In conclusion, anti-tumor responses were durable and continued after Nivolumab-treatment discontinuation.
Next phase of clinical trials will further assess the significance of Nivolumab on survival in patients with ovarian cancer. ( Xagena )
Hamanishi J et al, J Clin Oncol 33, 2015 (suppl; abstr 5570)