Interview With Michael B. Atkins, MD

Immunotherapies in Melanoma: Taking Stock

Alice Goodman, MA; Michael B. Atkins, MD

Disclosures

July 02, 2012

Editor's Note:
Immunotherapy is the only treatment that can produce durable tumor regression in patients with metastatic melanoma. With novel molecularly targeted agents also being developed for metastatic melanoma, the hope is to learn how to combine and sequence these therapies and improve survival for patients with this once universally fatal disease. At the 2012 annual meeting of the American Society of Clinical Oncology (ASCO®), Dr. Michael B. Atkins, Deputy Director of the Georgetown Lombardi Comprehensive Cancer Center in Washington, DC, chaired an educational session on immunotherapy in advanced melanoma. Medscape caught up with Dr. Atkins to ask him to put into perspective the emerging data on immunotherapy and what questions still need to be answered.

IL-2 Opens the Door

Medscape: What was the first immunotherapy to show an effect in metastatic melanoma?

Dr. Atkins: High-dose interleukin (IL)-2 received US Food and Drug Administration (FDA) approval for the treatment of patients with metastatic melanoma in 1998. A number of durable responses were observed and 11% of patients were alive at 5 years.[1] More recent studies have shown that patients with elevated lactate dehydrogenase (LDH) levels are much less likely to respond to IL-2, with about a 6% response rate in patients with elevated LDH (all partial responses) and about 21% in those with normal LDH levels.[2] Analysis of molecular profiles shows that a significantly larger proportion of patients with BRAF- and NRAS-mutated tumors respond to IL-2 than those who do not have these mutations.

Also, we now have information suggesting that tumors with an inflamed phenotype and immune infiltrates have a 2- to 3-fold improved chance of response relative to those with a noninflamed gene expression pattern.

Michael Atkins, MD

Medscape: Has IL-2 been combined with other immunotherapies?

Dr. Atkins: IL-2 has been combined with vaccine therapy. Results of a randomized trial found that the combination of IL-2 plus vaccine produced response rates of 22.1% compared with 9.7% with IL-2 alone, and a trend was observed toward improved overall survival.[3] Median survival was 17.6 months with the combination of IL-2 plus vaccine vs 12.8 months with IL-2 alone. Very few relapses were seen beyond 2 years in responding patients, a hallmark of effective immunotherapy. However, lower-than-expected response rates were reported for the IL-2-alone group, calling into question how much of an advance this treatment is.

Some questions remain: Is this a proof of concept that the immune response can be focused by a vaccine? Will the findings be relevant with novel immunotherapies?

Ipilimumab: A Check-Plus for a Checkpoint Inhibitor

Medscape: More recently, ipilimumab, a different type of immunotherapy, was approved by the FDA for the treatment of metastatic melanoma. This drug is referred to as the first checkpoint inhibitor, meaning that it interferes with an important downregulatory property of the immune response. How does this drug work, and what kinds of outcomes does it achieve?

Dr Atkins: The monoclonal antibody ipilimumab blocks CTLA-4, which serves as a coregulatory protein that shuts off the immune response when it binds to a protein on antigen-presenting cells. Blocking CTLA-4 restores immunity. Ipilimumab has been evaluated in a variety of clinical trials. It is administered intravenously once every 3 weeks for 4 doses on an outpatient basis. Its side effects result primarily from induction of immune reactions against normal tissues, but in general, it produces fewer inflammatory systems (eg, fever, chills, hypotension) than those associated with high-dose IL-2.

A recent trial compared ipilimumab plus gp100 vaccine vs ipilimumab alone vs the vaccine alone.[4] In both ipilimumab-containing arms, survival was prolonged. One-year survival was 46%, 44%, and 26% for the 3 arms, respectively. Two-year survival was 22%, 24%, and 14%. Few deaths occurred in the ipilimumab-treated patients after 30 months.

Medscape: What about the safety profile of ipilimumab and patient selection?

Dr Atkins: The toxicities of ipilimumab are related to activation of the immune system and include colitis, dermatitis, endocrine effects, and hepatitis.

In clinical trials, all subgroups benefitted from ipilimumab, with the possible exception of patients with elevated LDH. One feature of ipilimumab is apparent disease progression early in the course of treatment followed by a major response, so we have learned that the effect of treatment is not seen immediately.

Pooled data from clinical trials suggest that about 25% of patients with metastatic melanoma have long-term benefit from ipilimumab therapy, and the benefit might be greater with a higher dose of the drug. Also, there is a potential role for maintenance therapy with this agent.

Medscape: Has ipilimumab been studied in combination therapy?

Dr Atkins: A study was conducted in previously untreated patients with metastatic melanoma in which the patients were randomly assigned to dacarbazine alone or dacarbazine plus ipilimumab.[5] Some experts expected better results than were achieved in this first-line setting, and it is possible that dacarbazine may have compromised outcomes.

Medscape: What are the take-home messages about ipilimumab for metastatic melanoma?

Dr. Atkins: Ipilimumab enables an immune response and antitumor responses in some individuals. This agent is powerful enough to work in the central nervous system and overcome concurrent immunosuppression. The response to ipilimumab may be associated with autoimmunity. Activity of the drug is seen in patients previously treated with IL-2. This drug is an option for most patients with advanced melanoma. Optimal timing of therapy and severe autoimmune toxicities should be considered.

We don't know the answers to all of the questions about how to use ipilimumab. Should it be combined with dacarbazine? Should it be used as first-line or second-line treatment? What is the optimal dose and schedule? Does it have a role in maintenance therapy? What is its role in the adjuvant setting? What combinations should be studied? Some possible combination partners are bevacizumab, GM-CSF [granulocyte-macrophage colony-stimulating factor], high-dose IL-2, and the novel PD-1 antibody.

PD-1 Inhibitor: New Kid on the Block

Medscape: At the 2012 annual meeting of ASCO®, we heard exciting preliminary reports about a second checkpoint inhibitor called MDX-1106, a PD-1 antibody. How does this immunotherapy work, and what are preliminary observations?

Dr. Atkins: On activated T-cells, PD-1 serves as the receptor for PD-L1, which is expressed on tumor cells. When PD-L1 binds to PD-1 inside the tumor microenvironment, it paralyzes T-cell immune function. Blocking the interaction between PD-L1 and PD-1 with an antibody provides a specific way to activate the immune system within the tumor microenvironment. It is hypothesized that this would provide a less toxic and more potent means of activating the immune system.

Several presentations at ASCO® on this novel immunotherapy showed exciting preliminary results. A large phase 1 study evaluated MDX-1106 given every 2 weeks for up to 2 years in patients with melanoma, renal, and non-small cell lung cancer.[6] Durable responses were seen in all 3 malignancies. In the melanoma patients, about half had tumor shrinkage and some responses were quite significant. This novel therapy will move forward in clinical development for patients with melanoma, either as a single agent or in combination. A number of PD-1 and PDL-1 blockers are under development.

Which Patients Are Right for Immunotherapy?

Medscape: How do you select patients for treatment with immunotherapy?

Dr Atkins: Patients with metastatic melanoma are not all the same. There are 2 basic phenotypes: noninflamed and inflamed.

Data suggest that the second phenotype is associated with a better prognosis; that is, the greater the percentage of immune cells within a tumor, particularly CD8+ T cells, the better the prognosis.

As mentioned previously, patients with tumors expressing an immune signature are more likely to respond and to exhibit a longer progression-free survival than those with tumors that do not have this signature.

Studies suggest that PDL-1 expression appears to be associated with benefit, because patients without PD-L1 expression were less likely to respond to PD-1 antibody.[6,7,8]

Sequencing: Which Therapy, and When?

Medscape: What is the current thinking on sequencing of therapies?

Dr Atkins: In addition to immunotherapies, several new targeted therapies are on the horizon. Vemurafenib, which targets tumor containing a BRAF V600E mutation, is approved for the treatment of patients with metastatic melanoma, and other BRAF and MEK inhibitors are being studied. These therapies may be able to be used in combination with immune therapies to improve outcomes.

Most patients would like a chance to be cured. Immune therapies are the only curative therapies for advanced melanomas. Thus, if patients can receive an immune therapy, it may be better to give it first. For BRAF wild-type tumors (those without the BRAF V600E mutation) and even for the BRAF-mutated tumors, it might make sense to give patients an immunotherapy first to try to produce long-term benefit and reserve the use of a BRAF inhibitor for those patients who don't respond to immunotherapy.

Data suggest that giving an immunotherapy first does not reduce the ability to respond to a BRAF inhibitor. On the other hand, patients who progress on vemurafenib do not appear to respond to ipilimumab. In fact, in a small study of 32 patients whose disease progresses on vemurafenib, 50% were dead within 4 months.[9] Only 3 of the 32 patients were alive longer than 1 year, and all of them were back on a BRAF or a MEK inhibitor.

These preliminary data suggest that a BRAF inhibitor may not be the best initial therapy for some, if not most, patients with BRAF V600E mutations. A prospective trial is needed to study this question. A sequencing study is being planned by ECOG that has 2 arms: ipilimumab with crossover to vemurafenib at time of progression vs vemurafenib with crossover to ipilimumab at time of progression. The primary endpoint will be overall survival at 2 years. The study should tell us which is the best initial therapy for patients with BRAF mutant metastatic melanoma.

More Work to Be Done

Medscape: Are there any potential downsides to combining immunotherapy and targeted therapy?

Dr Atkins: By combining immunotherapy and targeted therapy, the hope is to get the benefits of both worlds. But there are potential problems. Studies suggest that dacarbazine interferes with the immune effects of ipilimumab; however, preliminary data suggest that BRAF inhibitors might increase immune infiltration into tumors, converting the microenvironment from a noninflamed state to an inflamed state. Theoretically, this might mean that the combination of a BRAF inhibitor with immunotherapy might produce synergistic antitumor benefits.

Medscape: What can you say to sum up where we are with melanoma immunotherapy in 2012?

Dr Atkins: We have IL-2 and ipilimumab, and there are novel immunotherapies on the horizon, including the PD-1 antibody. We will need studies to refine optimal patient selection and identify the best combination treatments, including a BRAF inhibitor either alone or in combination with MEK inhibitors. The field has advanced, and in 2012 it is no longer futile to treat metastatic melanoma. There is a glimmer of hope on the horizon, but there is still a lot of work to be done.

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