Transcript:Adam M. Brufsky, MD, PhD: We have an abundance of riches. We have ribociclib, and we have palbociclib. How do we decide? Kim, you are on one of the MONALEESA trials. What’s your experience with ribociclib?

Kimberly L. Blackwell, MD: Well, my honest answer is the drug that’s the easiest for my patient to get and the easiest for me to get for the patient is probably going to be my choice. So, things like co-packaging the CDK inhibitor with the AI, dosing, and central pharmacy versus a specialty pharmacy, I think they’re the things that really make an impact on a practice.

We’re all busy practicing physicians, and anything that reduces the confusion, improves compliance, and reduces the stress helps. I tell a patient, “Oh, you’ve got to take these 2 pills,” and then they go to the pharmacy and find out it’s going to be a 3-week wait and they have to sit on hold for 2 hours. It has created a stress in the clinic, so I’m looking for all of the companies that make these to really help us get these very effective drugs to our patients. That’s my honest answer. Obviously, if one of the studies, as they mature, shows that there’s a survival advantage or that there’s really some absence of toxicity we saw with other drugs, that will influence my decision. But right now, I just don’t see a huge difference with the data we have across the drugs.

Debu Tripathy, MD: From the standpoint of mechanism of action, toxicity, and efficacy, ribociclib and palbociclib are very similar.

Adam M. Brufsky, MD, PhD: Look at the curves—they’re identical.

Debu Tripathy, MD: There is the issue of cardiac conduction and QTc prolongation with ribociclib, which does require more monitoring. The rare transaminitis requires monitoring. Ribociclib is a little easier to dose-adjust, though, because it’s 600 mg and it comes in 200 mg capsules. They each have their pros and cons, and I agree with Kim. At the end, for different centers—depending on how they’re set up—and insurance companies, it’s going to really be what makes it easier for the patient. Now, abemaciclib is pharmacologically different.

Adam M. Brufsky, MD, PhD: Right, which we’ll get to in a second. We have a lot of really good translational biologists sitting at this table. But before we go back to ribociclib, this question just came up: Are we believers in this Ki-67 drop as a surrogate? We’re believers in it?

José Baselga, MD, PhD: Absolutely. In ER-positive disease, for every single study that has been shown to be positive, the Ki-67 has been a great marker of an effect. We saw that initially in the adjuvant studies with everolimus. We saw that in the combination studies with anti-ER therapies. We see it now with CDK4/6 inhibitors, so I think it’s very important right now.

Adam M. Brufsky, MD, PhD: Good. So, that’s good for people now.

Carlos L. Arteaga, MD: It’s also a good way of triaging negative trials, like the gefitinib and Arimidex (anastrozole) trials. They did not work in the metastatic setting. Sometimes, you can use it to almost predict metastatic studies that you should or should not do.

Adam M. Brufsky, MD, PhD: That’s a very good point. Basically, what I’m hearing from everybody is that these drugs are similar. It’s really going to depend on a lot of potentially non-clinical issues or non-efficacy toxicity issues to note the difference between ribociclib and palbociclib at this point in time. I think those are reasonable things. It’s good that we have more options for patients now. It’s better to have more than one.

Kimberly L. Blackwell, MD: I think it’s important to point out, though, that there are going to be a lot more data with each of these agents. So, for the general practitioner right now, what we are saying applies to 3 large randomized trials: PALOMA-2, PALOMA-3, and MONALEESA-2. But there are about 15 MONALEESA studies with ribociclib, and I’m sure there are 15 or more with palbociclib. As educated providers of these drugs, we’ll have to stay on top of all of the studies as they emerge.

Transcript Edited for Clarity