Dr. Monty Pal and Dr. Atul Batra discuss the PLANeT study from India, which evaluated low-dose pembrolizumab in addition to neoadjuvant chemotherapy for triple-negative breast cancer, and its place among a growing body of international research on improving efficacy while reducing costs and toxicity with lower doses of immunotherapy.

TRANSCRIPT

Dr. Monty Pal: Hello and welcome to the ASCO Daily News Podcast. I'm your host, Dr. Monty Pal. I'm a medical oncologist, professor, and vice chair of academic affairs at the City of Hope Comprehensive Cancer Center, Los Angeles.

My guest today, I think, is going to be a really riveting one. It's Dr. Atul Batra, who is an additional professor of medical oncology at the All India Institute of Medical Sciences, or AIIMS, in New Delhi. And he's also the senior author of the PLANeT study. It's a very compelling study that evaluated low-dose pembrolizumab in addition to neoadjuvant chemotherapy for triple-negative breast cancer. And it's really a big part of a growing body of research that's showing balanced efficacy when we use lower doses of immunotherapy instead of standard doses to reduce cost, as well as potentially toxicity. I think this has huge implications for our global audience, and I'm so thrilled to have you on the podcast today, Dr. Atul Batra, welcome.

Dr. Atul Batra: Thank you, Dr. Pal.

Dr. Monty Pal: And we'll just take it with first names from here since we're both friends. I have to give the audience some context. Atul, I had the great honor of visiting AIIMS New Delhi. For those that don't know, this is really, you know, the Harvard Medical School of India. It's the most competitive institution for medical training. And on the back end of that, there's also incredible resources when it comes to clinical trials and infrastructure. I just wanted to have you give the audience sort of a scope of the types of trials that you've been able to do at AIIMS New Delhi.

Dr. Atul Batra: Thank you, Monty. So, I work at the All India Institute of Medical Sciences, and we had the honor and pleasure of having Monty here this month. And people are still in awe of his lectures that he delivered there.

Coming back to our institute, so it's kind of a medical college. It's one of the oldest ones, it was built in 1956. We are lucky enough that we get the best of the residents and fellows because they have to go through an exam, a competitive exam, and mostly it's them who come to us and we're able to do some good work out here.

Regarding the trials that we have conducted, we do conduct some investigator-initiated studies, and we try to answer the questions where we can help our own patients. Like, for example, this PLANeT study. Every other patient in the clinic was almost not able to afford Keytruda at the full dose, pembrolizumab, and we had a lot of evidence creeping in that a lower dose might be helpful. And that's how we planned this study.

Before that, there are certain cancers that are peculiar to India, like gallbladder cancer, head and neck cancers. These are much more common in India as compared to the U.S., and there are some good studies that have been conducted from our own institute by our senior colleagues which have been presented at ASCO and published in the JCO.

We also did the capecitabine hand-foot syndrome study that was known as the D-ToRCH study: 1% diclofenac gel that became the standard of care to prevent hand-foot syndrome.

So, that's kind of a brief overview of investigator-initiated studies. India is slowly and steadily becoming a partner of the global registration trials. And it's more recently, the last five years or so, we have seen that the number of phase 2 and phase 3 trials are increasing and we are able to offer now these trials as well to our patients.

Dr. Monty Pal: That was a terrific overview. I just want to highlight for the audience, as we go through some of your discussions today around specific trials, the speed at which this can be done. Just for context, for me to accrue a clinical trial of 30 patients – I think many people have probably come across some of the work that I've done in the microbiome space – at a single institution, 30 patients, right, takes me about a year and a half, two years. We're going to go through some trials today where Dr. Batra and his team have actually, in fact, accrued close to 200 patients over a span of just a year, which is just remarkable by, I would say, any American standard.

So, I see a real need for partnership and Atul, I'll kind of get back to that at the end. But without further ado, the focus of this podcast today, I think, is really this terrific presentation you gave in an oral session at ESMO and subsequently published in Annals of Oncology related to the PLANeT study. Would you give the listeners some context around what the study entailed and population and so forth?

Dr. Atul Batra: So, we know the KEYNOTE-522 became the standard of care for triple-negative breast cancer, where Keytruda, when added at 200 mg, the standard dose every three weeks with neoadjuvant, increases the pCR from around 51% to 64% by a magnitude of around 13%. However, in India and other low-middle income countries, less than 5% of the patients actually have access to this dose of pembrolizumab.

So, our standard of care was actually just chemotherapy till now. And this kind of led us to design this trial. There are data that come from previous trials conducted in India, from the Tata Memorial, done in head and neck space, some other studies done in Hodgkin's lymphoma, that a much lower dose, probably around one-tenth of the dose, works well in these cancers.

So, that's where we designed the PLANeT study, where we gave the standard neoadjuvant chemotherapy in the control arm, and in the experimental arm we added 50 mg of pembrolizumab. This was given every six weeks for three doses. So, that's a total of 150 mg over the neoadjuvant period as compared to 1,600 mg that was given in the KEYNOTE-522 study. So, this was almost one-tenth of the study.

Dr. Monty Pal: So, a tenth of the dose, which is just remarkable. I mean, that's just such an interesting concept.

Dr. Atul Batra: And the results, when we – the primary outcome, this was a phase 2 study. We just wanted to see, is there a signal of activity? And to even our surprise, when we looked at the pathological complete response rates, in the control arm this was 40.5%, and in the experimental arm this was 53.8%. So, a difference came to around 13.3%; it was numerically, I mean, so much similar to what KEYNOTE-522 had with just these many doses.

So, this was around 160 patients randomized over one year. We could randomize them in one year because of the load that we see. And the primary endpoint was met, and we could see that the path complete response did show a remarkable increase. We are still following these patients to see whether there is a difference in event-free survival at a longer follow-up. Until now, it's a small follow-up, so the number of events absolute, are different: four events in the experimental arm and 11 events in the control arm. So, we are seeing some signal even in this much short follow-up period as well. But we need to see more of what happens in the longer term.

Dr. Monty Pal: That's so impressive. I wonder, with this lower dose, do you attenuate toxicity at all as far as you can gather?

Dr. Atul Batra: So, although we shouldn't be doing kind of cross-trial comparisons, but if you look at thyroid dysfunction, we saw that around 10% of our patients had this thyroid dysfunction. This was compared to 15% in the KEYNOTE-522, that was a larger sample size though. But we're seeing that all the toxicities are somewhat less as compared to those in the standard dose. So, the exposure is less, but I mean, I can't really commit definitely on this. For this we would need much more data to say this with more confidence.

Dr. Monty Pal: Yeah. I'm going to ask you a really tough question to follow up, and this is probably something that's on everyone's mind after reading a study like this. Is this something that is disease-specific that needs to be replicated across other histologies? The reason I ask this is, you know, you think about paradigms like, for instance, in the States we're toying between intravenous versus subcutaneous delivery of checkpoint inhibitors, and we have studies focused in specific histologies that might justify use across all histologies. With this particular phenomenon, do you think we need to do dedicated studies in renal cell or in colon cancer and other places where, you know, in selected settings we might use checkpoint inhibitors and then decide whether or not there's this dose equivalence, if you will?

Dr. Atul Batra: That's a real tough one, though. But I'm happy to share that there are several ongoing studies within India currently. At our institute, my colleagues are leading studies in lung cancer space, cervical cancer. There was already a publication from Tata Memorial Hospital in head and neck cancers and we see that the signal has been consistent throughout.