November 12, 2018
Genomically Targeted Therapies in Neuro-Oncology
Interview with Dr. Wick
Dr. Gaines: So you’re presenting at a session at a special symposium on brain tumors here at ESMO this year. Can you tell me what is meant by genomically targeted therapies?
Dr. Wick: It’s in essence similar in all parts of oncology. So you’re looking for a lesion, mainly in the DNA, but sometimes also in some specific pathways, specific proteins, which helps you to identify a treatment, which then would be pretty specific for that lesion. And if that lesion is really a driving force in the proliferation or some resistance mechanism in the tumor, it should help to target that specific tumor. The lesions sometimes are broad across multiple tumor entities, so you would have a lesion which is relevant in different cancers, including brain tumors, or you would have a lesion which is specific for a particular disease.
If you have a lesion, which is across multiple entities, you may have this lesion in a very personalized fashion in one patient with a specific tumor, let’s say a glioblastoma patient has a specific BRAF alteration.
That same BRAF alteration is also seen in skin cancer and some lung cancers, but only in a very small percentage of brain tumor patients. Knowing what this genetic lesion is, be it a fusion, be it whatever genetic alteration would help you to identify a very specific treatment. If you have this specific treatment, it should work in this specific patient but not in all the many other patients without that specific lesion, and it should help you to enhance efficacy, potentially also avoid side effects, and have, at least for some time, a pretty good treatment for the patient.
Dr. Gaines: Can you tell me about a specific type of therapy, this type of therapy in neuro-oncology?
Dr. Wick: I think what is attractive in neuro-oncology these days, starting at the lower grade tumors, is the IDH alterations. So we have a mutation in the isocitrate dehydrogenase gene, which is leading to a very conserved alteration of the pathway, which is relevant for low-grade tumors. IDH1 mutations but also IDH2 mutations, which are relevant for leukemia, are targeted by small molecules and those targeted small molecules are effective in leukemia, are, in fact, approved in leukemia and we hope of course that in these lower-grade tumors the specific targeting of the IDH mutation is also helpful for patients.
Dr. Gaines: Now, what literature exists to support such therapies?
Dr. Wick: So far, there is a lot of basic research. So we have marvelous publications on the exact function of IDH mutations, for example. So we know that the IDH mutation is changing the epigenome of cells, so making the cells specific, causing a certain vulnerability to treatments.
We know that this is leading to a very specific type of brain tumor, so all lower grade tumors and aplastic tumors are either IDH mutated or not. And if they are IDH mutated, they are developing in a very specific way. And there’s uncontrolled data so far, showing that potentially, specifically, the patients with these lower-grade lesions not already transformed into an androgenic high-grade intensively contrast enhancing tumor are benefiting from this treatment.
Dr. Gaines: Tell us about some therapies that are currently under investigation.
Dr. Wick: I think what is attractive at this point in time is molecules that are, again, targeted. So you have, as a target, for example, the EGFR amplification or the EGFRvIII mutation, so a specific alteration. You have a linker between an antibody and a toxin.
For example, in the molecule ABT414, which is currently under development both in recurrent glioblastoma and in newly diagnosed glioblastoma, specific for this 25% of patients that harbor those EGFR alterations and then it will be coupled to the tumor cells with this receptor, taken up by the tumor cell, and then the toxin is liberated in the tumor cell and will act just specifically in those labeled tumor cells, one.
Second, I think, as in many other diseases, we are looking for the efficacy of checkpoint inhibition. There are multiple checkpoint inhibitors under development targeting PD-1, targeting PD-L1, targeting CTLA-4. We are focused more on the PD-1/PD-L1 axis in neuro-oncology.
There has been a trial at recurrent glioblastoma which was comparing head to head with bevacizumab and nivolumab. This trial was not showing an increased efficacy of nivolumab over bevacizumab, which is approved in the United States for recurrent glioblastoma (not in Europe). Therefore, this trial will not lead to a path forward for this particular agent.
The newly diagnosed trials are just underway. They are control trials, standard of care, radiochemotherapy with temozolomides plus/minus nivolumab or placebo. Honestly, hopefully, we will see something in these trials.