Vitrakvi approved for NTRK+ cancers | MyOncoPath

FDA approves Vitrakvi in all tumor types with NTRK gene variants

Progress continues in the area of personalized cancer treatment and tumor profiling. Now a distant memory, in 2017 the FDA approved Keytruda (pembrolizumab) for use in any cancer diagnosis showing high levels of microsatellite instability (MSI) or mismatch repair deficiency (MMR). This was a huge advancement in treatment based upon the genetics (and not the location) of cancer; Keytruda had previously only been approved for use in certain cancers such as lung cancer and head & neck cancer.

Late last year, the second universal approval by the FDA was announced - another breakthrough in genetic oncology. Vitrakvi (larotrectinib) was approved for use in any solid tumor harboring a NTRK variant (NTRK1, NTRK2, & NTRK3 genes). Variants in NTRK aren't too terribly common, but cancers with NTRK variants (primarily NTRK gene fusions) are highly oncogenic, meaning they promote cancer/tumor growth. Because NTRK variants have been found in a wide variety of tumor types, use of a basket trial to study response to NTRK inhibitors was a highly effective study design.

What's a basket trial?

Good question. It's honestly exactly what you might be thinking - you just dump all sorts of cancer types in one basket, or treatment approach. Alternatively, some studies dump patients into a specific arm of a study based upon their tumor type or genetic mutation - those are umbrella trials. Basket trials are great options in situations where we know that certain genetic variants are tumor-agnostic, meaning they don't occur in one type of cancer, but rather, many. Because of the approach, many more people are eligible for basket trials, and if the results are promising, FDA approvals for targeted therapies like the one in this post can happen.

For this particular instance, the FDA based its approval on 3 separate clinical trials involving 55 patients with NTRK gene fusions in their tumors. Tumor types varied (see cropped image), but in these studies, the tumors themselves were inoperable or the tumors/cancers had gotten worse on the previous treatment. In the 55 patients who took Vitrakvi, 75% of patients showed improvement (shrinking of the tumor) which was completely amazing - and those results led to accelerated approval by the FDA.

Tumor types in 55-patient combined clinical trial

FDA clinical trial that led to approval of Vitrakvi for NTRK positive tumors: listing of tumor types in the trial

Now, there are limitations to this cancer treatment (cue the fast-talking at the end of the commercial). Fortunately in the area of side effects, there aren't many and the drug (a pill) is well-tolerated in the body. But there is evidence, even in the clinical trial that led to approval by the FDA, that Vitrakvi may not be the end-all, be-all treatment. At this point, it likely won't last/work forever in everyone it works in initially, as there are some mechanisms at play that ultimately lead to resistance to these so-called first generation TRK inhibitors. In the trials above, about 73% of patients still had improvement at the 6-month mark, and 39% showed improvement after 1 year. That's not horrible, but it isn't ideal either. Fortunately, next-generation TRK inhibitors are already being developed and some are in clinical trials now. So stay tuned.

Suggested links for more detail

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  1. Cocco, E, Scaltriti, M, & Drilon, A (2018). NTRK fusion-positive cancers and TRK inhibitor therapy. Clinical Oncology: 15, 731-47.
  2. Drilon, A. et al (2018). Efficacy of larotrectinib in TRK fusion-positive cancers in adults and children. NEJM: 378, 731–39.
  3. FDA Press Release (2017). FDA approves first cancer treatment for any solid tumor with a specific genetic feature. Link here.
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