Ipilimumab and a poxviral vaccine targeting prostate-specific antigen in metastatic castration-resistant prostate cancer: a phase 1 dose-escalation trial.
BACKGROUND
Therapeutic cancer vaccines have shown activity in metastatic castration-resistant prostate cancer (mCRPC), and methods are being assessed to enhance their efficacy. Ipilimumab is an antagonistic monoclonal antibody that binds cytotoxic T-lymphocyte-associated protein 4, an immunomodulatory molecule expressed by activated T cells, and to CD80 on antigen-presenting cells. We aimed to assess the safety and tolerability of ipilimumab in combination with a poxviral-based vaccine targeting prostate-specific antigen (PSA) and containing transgenes for T-cell co-stimulatory molecule expression, including CD80.


METHODS
We did a phase 1 dose-escalation trial, with a subsequent expansion phase, to assess the safety and tolerability of escalating doses of ipilimumab in combination with a fixed dose of the PSA-Tricom vaccine. Patients with mCRPC received 2×10(8) plaque-forming units of recombinant vaccinia PSA-Tricom subcutaneously on day 1 of cycle 1, with subsequent monthly boosts of 1×10(9) plaque-forming units, starting on day 15. Intravenous ipilimumab was given monthly starting at day 15, in doses of 1, 3, 5, and 10 mg/kg. Our primary goal was to assess the safety of the combination. This study is registered with ClinicalTrials.gov, number NCT00113984.


RESULTS
We completed enrolment with 30 patients (24 of whom had not been previously treated with chemotherapy) and we did not identify any dose-limiting toxic effects. Grade 1 and 2 vaccination-site reactions were the most common toxic effects: three of 30 patients had grade 1 reactions and 26 had grade 2 reactions. 21 patients had grade 2 or greater immune-related adverse events. Grade 3 or 4 immune-related adverse events included diarrhoea or colitis in four patients and grade 3 rash (two patients), grade 3 raised aminotransferases (two patients), grade 3 endocrine immune-related adverse events (two patients), and grade 4 neutropenia (one patient). Only one of the six patients previously treated with chemotherapy had a PSA decline from baseline. Of the 24 patients who were chemotherapy-naive, 14 (58%) had PSA declines from baseline, of which six were greater than 50%.


CONCLUSIONS
The use of a vaccine targeting PSA that also enhances co-stimulation of the immune system did not seem to exacerbate the immune-related adverse events associated with ipilimumab. Randomised trials are needed to further assess clinical outcomes of the combination of ipilimumab and vaccine in mCRPC.


BACKGROUND
US National Institutes of Health.
Laboratory of Tumor Immunology and Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Ravi A
RA
Madan
Mahsa
M
Mohebtash
Philip M
PM
Arlen
Matteo
M
Vergati
Myrna
M
Rauckhorst
Seth M
SM
Steinberg
Kwong Y
KY
Tsang
Diane J
DJ
Poole
Howard L
HL
Parnes
John J
JJ
Wright
William L
WL
Dahut
Jeffrey
J
Schlom
James L
JL
Gulley
D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D015703:Antigens, CD / Q000276:immunology; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D019496:Cancer Vaccines / Q000276:immunology / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D016233:Immunotherapy, Active; D000074324:Ipilimumab; D008297:Male; D008875:Middle Aged; D009919:Orchiectomy; D011212:Poxviridae / Q000276:immunology; D017430:Prostate-Specific Antigen / Q000276:immunology*; D011471:Prostatic Neoplasms / Q000276:immunology / Q000556:secondary / Q000628:therapy*; D014765:Viral Vaccines / Q000276:immunology / Q000627:therapeutic use*
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000970:Antineoplastic Agents; D019496:Cancer Vaccines; D000074324:Ipilimumab; D014765:Viral Vaccines; D017430:Prostate-Specific Antigen