Collaborative Roles in Managing Toxicities and Supporting Patients on CDK4/6 Inhibitors

In this Pharmacy Times interview, Heather Moore, PharmD, BCOP, CPP discusses the collaborative nature of oncology care teams in managing patients on CDK4/6 inhibitors. She highlights the importance of clearly defined yet overlapping responsibilities among nursing assistants, nurses, advanced practice providers, pharmacists, and oncologists, all working toward the shared goal of optimizing patient outcomes. Moore emphasizes how nursing staff play a key role in education and follow-up—particularly when patients experience adverse effects such as diarrhea with abemaciclib—while pharmacists contribute expertise in identifying drug-drug interactions, monitoring, toxicity management, and supportive care strategies. Together, these efforts ensure that patients receive comprehensive, well-coordinated care.

Pharmacy Times: What are the key survival outcomes that make CDK4/6 inhibitors the backbone of HR+/HER2– breast cancer therapy?

Heather Moore, PharmD, BCOP, CPP: So with CDK4/6 inhibitors—palbociclib, abemaciclib, and ribociclib—they've been integrated into our clinical practice based on the progression-free survival and overall survival that we've seen from the MONARCH studies, the MONALEESA trials, and the PALOMA trials. I think what we've seen is that, with all of the MONALEESA studies, there has been statistically significant overall survival. We've also seen that with MONARCH 3, and we have seen it in our real-world data with CDK4/6 inhibitors, letting us know that this makes sense in terms of where we integrate this as our first-line therapy for hormone receptor–positive metastatic breast cancer.

Pharmacy Times: Can you walk us through your approach to managing drug-drug interactions with CDK4/6 inhibitors, especially in patients on multiple therapies?

Moore: So I think in terms of drug-drug interactions, we really have to think about this from a pharmacodynamic perspective and then a pharmacokinetic perspective. In the setting of pharmacokinetic, or PK, drug-drug interactions, that’s when we’re really thinking about CYP3A4 and our PGPs. All three of our CDK4/6 inhibitors are CYP3A4 substrates, and ribociclib is also a CYP3A4 inhibitor.

So it’s really about being mindful of drug-drug interactions. Do we need to modify the dose? Sometimes this may impact the selection of the drug that we’re choosing. But I also think it’s important to be cognizant of pharmacodynamic, or PD, drug interactions, especially when thinking about the overlap of toxicities. This is particularly relevant with CDK4/6 inhibitors in the setting of ribociclib and QT prolongation.

We know that ribociclib can cause QT prolongation, and this can be compounded in metastatic patients who may also be on medications for pain, anxiety, depression, or other supportive care therapies, where we can see an increased overlap of QT prolongation. That’s why it’s really important that when we’re starting patients on CDK4/6 inhibitors, we look through their medication list and identify drug interactions.

Sometimes this may help in selecting a CDK4/6 inhibitor. For instance, if you have someone with a cardiac history who is on antiarrhythmics, ribociclib wouldn’t be appropriate. If you have someone who already has prolonged QT because of their pain medications or anxiolytics, then again, ribociclib might not be the best option. In other cases, in the setting of dose modification, if someone is on a concurrent therapy, we may just reduce the dose when initiating their CDK4/6 inhibitor to account for that interaction.

Pharmacy Times: How can pharmacists collaborate with oncologists and nurses to ensure safe and effective therapy management?

Moore: I think this is such a general question, but also a very important one. With all of our care team members—whether that be our nursing assistants, nurses, APPs, pharmacists, or medical oncologists—we all have such important roles, but our goal is ultimately the same, and that is providing the best care for the patient. Sometimes our roles and responsibilities can overlap, but it’s important to have an idea of who is doing what and how we can integrate so that we provide better care.

I think of nursing as having a strong responsibility in terms of patient education, but also follow-up. For example, when we’re starting patients on agents like abemaciclib, which we know can cause significant diarrhea or GI toxicity, it can be helpful to have touchpoints. It’s valuable for our nursing team to follow up with patients and reinforce some of the mitigation and management strategies that were already discussed with them, whether that came from the pharmacy team, medical oncology, or other members of the care team.

From the pharmacist’s perspective, we have many roles and responsibilities and a lot of opportunities to support care. Much of that includes identifying drug-drug interactions, monitoring, and toxicity management, as well as having touchpoints with patients. Pharmacists can also provide insight into the best supportive care strategies.

Ultimately, I think we all work together to provide the best possible care for our patients.