Margaret von Mehren, MD: Regarding my personal experience with ripretinib, I’ve been fortunate to be able to participate in the phase 1 study, in particular the dose expansion part, where the dose was known and we were trying to check and see what activity was seen. I participated in the phase 3 INVICTUS trial [NCT03353753], and currently I am also participating in the phase 3 trial that is evaluating ripretinib versus sunitinib. The results are not known because the study is not finished. However, in general, as I’ve said, while I’ve listed and talked about adverse effects that the drug can have, I think most patients tolerate the drug very well. I have some patients who are continuing on the drug for more than 2 years and have been able to tolerate it without major adverse effects that limit their ability to do what they want to do. It’s been gratifying to see patients in whom the disease has been controlled and even patients with tumors that have decreased in size. Certainly, from the INVICTUS data and the phase 1 data, the number of patients whose tumors shrank is less than 10%. That is on a par with what we see with Sutent [sunitinib] and regorafenib. I think it’s sort of in that same ballpark.
In terms of tolerability, in general, it is well tolerated, on par with or better than the things that we think about in second- and third-line therapy. The real art of medicine for patients with gastrointestinal stromal tumors [GIST] is working with them to make a dose of therapy, of a drug, work for them. Certainly, studies look at using “X” dose of a drug in a certain way, but with time and experience, I think learning how to start a drug, titrate it up to where patients can tolerate it, are important. In my experience with ripretinib, less of that needs to be done. Patients really can tolerate 150 mg, for the most part. And then, if the disease has progressed and they need to, they can tolerate 150 mg twice a day. So I think it’s been, from my perspective, a very easy drug to use, and I think patients have found it to be very tolerable. One caveat of this drug is hair thinning, which is quite different from many of the other drugs that they’re on.
The patient in the case was treated with ripretinib as fourth-line therapy. That is now available based on the FDA approval from May 2020. I think that’s a very appropriate use of this drug, and I would expect that this will likely be what many physicians will choose for their patients. Avapritinib, as we know, was also recently approved, although the indication for its approval was much more narrow—for patients with the D842V [PDGFR-α]-mutation. Interestingly enough, the drug, when it was developed in the phase 1 setting, was tested not only in patients with that specific mutation, but also in patients with KIT mutations, and there are some patients who benefit.
We know that this drug was tested and there was a recent release in the media of the study comparing it with regorafenib. The end point that was being evaluated was progression-free survival. Investigators looked to see whether avapritinib would be even better than regorafenib. Based on the news release, that was found not to be the case. We haven’t seen that data, so it’s a little bit hard to comment on what this study means and what the implications are. But in my mind, based on data from the phase 1 study, which I participated in, as well as in the phase 3 trial, I have seen some activity with that drug. So I would think that is a drug you may be able to utilize in this group of patients. The toxicities are similar to the kinases, with 1 exception: It does seem to have some toxicities of special interest. Of concern are issues with cognition, memory, which I think will have to be managed and handled carefully in patients. But I think avapritinib is a drug that may have a role for selected patients whose disease is progressing beyond the standard therapies that have been approved for KIT-mutant GIST.
Transcript edited for clarity.
Case: A 68-Year-Old Man With Gastrointestinal Stromal Tumor