NEW YORK – “Inject locally, treat globally” may become a new mantra for cancer immunotherapy. Dr. Ronald Levy, professor and chief of the department of oncology at Stanford (Calif.) University, discussed impressive and durable systemic results from local treatment of tumors, reviewing his group’s recent work and discussing ongoing early stage clinical trials.
In the hope of triggering an immune response that induces a systemic CD8 T-cell response, Dr. Levy and other investigators began experimenting with intralesional injections of immunotherapies, with and without adjunctive radiation or chemotherapy. The principle has been evaluated in a mouse model, in which up to 80% of mice receiving intratumoral immunotherapy were cured. Now, human trials are underway for solid tumors as well as lymphoma.
An early clinical trial involving 15 patients with recurrent low-grade B-cell lymphoma combined targeted low-dose radiation of a single tumor site with injection of CpG, immune-boosting snippets of DNA, into the same site. Looking for partial or complete regression, investigators saw promising results, though some patients who were responders didn’t see full effect until 24 weeks after injection (J Clin Oncol. 2010 Oct 1;28[28]:4324-32). The overall objective response rate was 27%, although 80% of patients (12 of 15) had stable disease or partial or complete response through a median follow-up of 33.7 months. Some individual patients had marked regression or disappearance of bulky tumors at distant sites.
CpG – motifs of cytosines and guanines – were strung together, said Dr. Levy, with a sulfur rather than a phosphate backbone to make them more stable for injection. These bits of DNA, which are present in both bacteria and vertebrates, are an agonist for toll-like receptor 9, activating B cells and dendritic cells, and then tumor-specific T-cells.
Dr. Levy and his collaborators used a two-tumor mouse model to track intralesional injection effectiveness for a variety of immunotherapies. Mice seeded with tumor cells bilaterally over the abdomen were injected with CpG and two other immune therapies at a single abdominal tumor site, and bilateral regression, if any, was tracked in comparison to systemic immunotherapy (J Clin Invest. 2013;123[6]:2447-63).
Though both treatment arms had good initial response, 70% of the systemically treated mice relapsed by 150 days after injection, compared with just 10% of those receiving intratumoral therapy (P = .002).
Of the 23 mice whose therapy consisted of intratumoral administration of CpG together with anti-CTLA4 and anti-OX40 antibodies (aCTLA4 and aOX40), 21 (91%) were alive 50 days after treatment. These mice fared better than did those receiving any other intratumoral treatment combination (P = .004, compared with CpG+aOX40; P = .03, compared with aCTLA4), suggesting a synergistic benefit to the triple combination.
Somewhat surprisingly, even murine models that also had tumor seeding into brain tissue saw marked reduction or even resolution of brain tumors, showing that the blood-brain barrier does not impede the effect within the CNS.
What didn’t work? PD-1 inhibitors were not particularly effective at provoking a systemic effect when injected into tumors. Peritumoral injection, though theoretically taking advantage of some aspects of the tumor microenvironment, also did not show global effect.
Based on the human CpG + radiation trials and the mouse experiments, the research group is proceeding with phase I and II clinical trials of CpG in combinations with aCTLA4 and aOX40. These, Dr. Levy said, were more likely to be available clinically, and human intratumoral T regulatory cells are known to express both CTLA4 and OX40.
All agents and combinations had an enhancing effect, said Dr. Levy. “We like this treatment and trial design,” he said, noting that everyone sees benefit at the local injection site, and some see global results.
Dr. Levy discussed multiple studies, and he disclosed receiving grant support from Pfizer, Dynavax, and Bristol-Myers Squibb. He also has served as a consultant to Five Prime, Kite, BeiGene, Innate Pharma, Bullet Biotech, and Immune Design.