Stephen M. Ansell, MD, PhD
Immune evasion is one of the biggest obstacles plaguing the implementation of checkpoint inhibitors into the treatment landscape of Hodgkin lymphoma, according to Stephen M. Ansell, MD, PhD.
at the 2018 Pan Pacific Lymphoma Conference, Ansell, chair of the Lymphoma Group at Mayo Clinic, discussed overcoming immune evasion in lymphoma.
OncLive: What is the issue with immune evasion in Hodgkin lymphoma?
One of the big challenges in lymphoma is that many immune cells are present right in the tumor, but somehow those immune cells are not killing the tumor cells. The key question is, how does the tumor hide from the immune system as efficiently as it does? Actually, there are many barriers to a good immune response in lymphoma. The cells that are there are pretty exhausted from being persistently activated, and sometimes there are other cells in the neighborhood that are suppressing their activity.
Also, there are many proteins that are being made on the tumor cell like cytokines, which activate the immune system but then exhaust it over time. With all that going on, plus the immune-suppressive macrophages present in the tumor, the real challenge is working out how to get the T cell to kill the tumor cell efficiently. There are a lot of strategies being tried to test that now.
What are some of the strategies?
One of the real successful strategies has been to prevent T-cell exhaustion. T cells basically get activated, make proteins such as PD-1 as a receptor on the cell surface, and that then puts them at risk for being suppressed by PD-L1 or PD-L2. Other receptors, such as TIM-3 and LAG-3, are important and those begin to increase as the cell becomes more exhausted. A strategy to keep the immune system engaged is to block these negative signals. Blocking PD-1 has been very successful in lymphoma, but now new trials blocking TIM-3 and LAG-3 are all in progress.
A second strategy that is proving to be very interesting is taking the macrophages, which are “bad boys” that are influencing the immune system in an unfavorable way, and getting them to turn on the tumor. The tumor puts a little protein on the cell surface that signals "don't eat me." The cell is really just telling the immune system that, “It is on their side.” But if you cover that up, the immune system—particularly the macrophages—will provide a lot more scrutiny of that cell and phagocytose it. That is another strategy that is proving to be very exciting and promising at this point.
How has implementing these strategies impacted patients with lymphoma so far?
The impact has been pretty profound so far. In Hodgkin lymphoma, blocking PD-1 has proved to be a significant success. Blocking PD-1 in patients who have had all treatments, including transplant or brentuximab vedotin, showed a response rate of at least 65% to 70%. That is now being used earlier in the disease course; in fact, it is even being combined with chemotherapy in the frontline setting. It has been shown that there is a high response rate as a single agent even if it is used before the chemotherapy. These are all ways that these strategies are becoming a reality and benefitting patients directly.
What would be your advice to clinicians facing the issue of immune evasion in their patients?
The exciting thing is that there are a lot of clinical trials in progress now. I encourage clinicians and patients to participate in trials, because that gives us answers that can impact practice down the road. Clinicians are very familiar with PD-1 blockade. They are using it across a broad spectrum of diseases, including solid tumors. However, the exciting part is the combination approaches—that is where the trials are in progress.
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