Atebimetinib (IMM-1-104) in combination with chemotherapy could represent a novel frontline treatment option for patients with metastatic pancreatic cancer, due to atebimetinib’s unique mechanism of action targeting MEK via intermittent deep cyclical inhibition, according to Martin F. Dietrich, MD, PhD.
“First-line therapy for [patients with] pancreatic adenocarcinoma is heavily dependent on chemotherapy. We’ve [also] come to understand the central role of KRAS [mutations] in driving the vast majority of pancreatic adenocarcinoma,” Dietrich, a medical oncologist at The US Oncology Network Cancer Care Centers of Brevard and an assistant professor of internal medicine at the University of Central Florida College of Medicine in Orlando, said in an interview with OncLive®. “The idea is to see if targeted therapy could augment and potentially synergize with chemotherapy in the first-line setting.”
In the interview, Dietrich discussed the present limitations of frontline chemotherapy for the treatment of patients with advanced/metastatic pancreatic cancer, the early-phase data that have been reported with the agent in this disease setting, and its future in the space.
OncLive: What are the current first-line chemotherapy regimens for patients with advanced/metastatic pancreatic cancer, and what are their limitations?
Dietrich: The current first-line standard of care for [patients with] pancreatic adenocarcinoma is dependent on the use of chemotherapy. We have a number of regimens that can be used, and they have to be tailored to the individual patient’s performance status and organ function. One of the standard regimens is gemcitabine [plus] nab-paclitaxel. It’s a doublet of 2 mechanisms that are used together, and it’s generally felt to be a bit milder [in terms of toxicity], but it also has limitations in regard to efficacy. The overall response rate [ORR] was [23%] with a [median] PFS of [5.5] months and a median OS of [8.5 months in the MPACT trial].2
We have 2 additional triplet regimens. We started out over 10 years ago with FOLFIRINOX [irinotecan plus oxaliplatin, leucovorin, and 5-fluorouracil (5-FU)], based on phase 2 data in France [NCT00112658]. We saw an ORR of 31.6%, a median PFS of [4.6 months], and a median OS of [11.1 months].3
Most recently, we had the readout of the [phase 3] NAPOLI-3 study [NCT04083235] that established NALIRIFOX [irinotecan liposome (Onivyde) with oxaliplatin, 5-FU, and leucovorin] against gemcitabine plus nab-paclitaxel. The ORR was 41.8% [95% CI, 36.8%-46.9%] and the [median] OS was 11.1 months [95% CI, 10.0-12.1].4
It’s a heavily chemotherapy-dependent treatment [paradigm]. We don’t have any more targeted therapies [approved] in the first-line setting. The limitations [of chemotherapy] are typically that although [these regimens] may be effective immediately, the concern is durability, not only from a standpoint of efficacy but also from a standpoint of cumulative toxicity. For nab-paclitaxel, we typically worry about cumulative neuropathy, in addition to cytopenias. For FOLFIRINOX and NALIRIFOX, the adverse effects [AEs] of concern are neuropathy from a different angle: the oxaliplatin-induced neurotoxicity. It is very different mechanistically from nab-paclitaxel, but similarly impactful.
There’s a lot of room for improvement [on frontline chemotherapy]. Unfortunately, many patients do not qualify for treatment at all, and there are also a lot of limitations with the durability of these therapies.
What is the mechanism of action of atebimetinib, and would you consider it to be novel, given its specificity for targeting MEK?
Atebimetinib has a unique mechanism of action. We have had MAP kinase inhibitors for a long time in the clinic, but their concept was very different. They were aiming at chronic suppression of MAP kinase signaling via direct targeting of MEK. We’ve had significant challenges, both in melanoma [as well as] colorectal and lung cancers where they are approved, with concerns for modulation of the immune system, fevers, and liver function test abnormalities. [These agents have also been] implicated in vascular integrity and vascular events.
The idea [with atebimetinib] is to target a very well-established and important pathway through a novel mechanism. The mechanism here is an intermittent deep inhibition mechanism that is labeled deep cyclical inhibition. This essentially allows for 2 things: We shut off the pathway long enough to allow for a synergistic effect on the efficacy side, but not long enough to induce significant traditional toxicities associated with MAP kinase inhibition.
[It’s a] very interesting concept. We never thought about this. We always thought ‘more is better,’ and the stronger the inhibition of a pathway target, the better. However, this doesn’t necessarily seem to be the case, and at least from the preliminary data that we have, both on a toxicity and efficacy side, the concept seems to be very promising.
How does the administration method of atebimetinib differentiate it from agents such as systemic chemotherapy?
Atebimetinib is an oral [agent]. It’s a different delivery of a therapy. It has a very interesting pharmacokinetic [profile]. We see an on/off activity off the MAP kinase pathway, but it seems to be enough to suppress tumor growth and avoid the escape pathways that we see with other MAP kinase [inhibitors]. It also avoids some of the typical MAP kinase AEs such as pyrexia.
What are the key design elements of the phase 1/2 trial evaluating atebimetinib in first-line pancreatic cancer?
This was a multicohort analysis that looked at atebimetinib in [patients with] pancreatic adenocarcinoma in 2 [groups]: in combination with gemcitabine and nab-paclitaxel and [in combination with] modified FOLFIRINOX [mFOLFIRINOX], as well as in combination with pembrolizumab [Keytruda] for [patients with] melanoma, [in combination with dabrafenib (Tafinlar) for patients with BRAF-mutated melanoma, and in combination with cemiplimab-rwlc (Libtayo) for patients with unresectable or metastatic, RAS-mutant non–small cell lung cancer].5 This is a broad investigation. It reflects how important the MAP kinase pathway is, either in the up-front propagation of cancer growth or in the resistance setting, so there’s broad interest [in atebimetinib].
Focusing on the benchmarks here in pancreatic adenocarcinoma, I believe it’s most important to understand the limitation that OS hasn’t exceeded 1 year in any significant way and the durability [of response] remains the main challenge [with chemotherapy alone]. We have early data [with atebimetinib], and they are data that we can contextualize very well historically against the efficacy data both for the doublet and the triplet chemotherapies. For practical purposes, the mFOLFIRINOX [data] are a more internationally accessible standard, [and the regimen] is in many ways similar to NALIRIFOX.
How did the early efficacy data with atebimetinib compare with historical benchmarks?
When we look at data from phase 1, and especially the results from the [phase] 2a part of the study, they set some very competitive benchmarks in the first-line setting for the use of atebimetinib in combination with chemotherapy. We saw that 94% of patients were alive at the 6-month high mark. This is a substantial increase in durability over the historical expectations.4
We [also] saw 70% of patients progression-free at 6 months, which signifies that the addition of atebimetinib is adding to the durability of the [chemotherapy] regimen in the first-line setting. This is certainly something that we don’t see with any of the other first-line chemotherapy regimens. There is a significant breakout of the survival curves.
We’ve seen some nice early responses that we would like to follow. The ORR was [approximately] double what we would typically see with first-line pancreatic adenocarcinoma treatment with gemcitabine and nab-paclitaxel, [and] many of these responses [were] deep and durable.
What has been observed regarding safety with the addition of atebimetinib to chemotherapy?
There’s always [a point] where we have to balance efficacy and safety. It’s very interesting to see that although we do see a mild increase in toxicity with gemcitabine and nab-paclitaxel being a backbone that is significantly better tolerated than our triplets, we don’t really see substantial increases when we look at the addition of atebimetinib in the first-line setting. This was a very favorable ratio of benefit to risk with this treatment, and certainly a de-escalation of toxicity from mFOLFIRINOX and NALIRIFOX.
It is also important to recognize that when we look at these datasets, the study looked at patients with less favorable [disease factors and characteristics]. They were typically older. We saw a patient population that was generally demonstrating all features of high-risk disease: CA 19-9 elevation, significantly high levels of liver and lung metastases, and a strong subset of peritoneal metastases. This was, if anything, a less favorable patient population in which these data were produced. [These findings] require verification in a prospective study, side-by-side with chemotherapy in a randomized fashion, but the first signal here [is] certainly incredibly strong.
What are the next steps that are needed in order for the combination to move forward?
It’s very clear that we have to do more for patients. There are 2 factors: One is the efficacy of the first-line therapy, and the other is the significant drop-off in the number of patients who are able to receive second-line [therapy]. The second-line options after exhausting first-line therapy, especially if patients start on a triplet in the first-line setting, [are sparse]. I believe that’s where atebimetinib is going to find a wide-open treatment opportunity.
This is a new mechanism, one that historically doesn’t have a side-by-side comparison. We’re using a well-established pathway in pancreatic adenocarcinoma, but with a new way of approaching it through intermittent deep cyclical inhibition that allows for a gain in efficacy, as the data would suggest, without a significant increase in toxicity. Most of the toxicity experience will remain defined here by the underlying chemotherapy backbone.
This presents opportunities, [including potential] combination options independent of the chemotherapy regimen. If you think about [how] we would normally like to offer fit and performance status–eligible patients a triplet in the first-line setting to maximize outcomes, maybe there’s an opportunity here of giving targeted therapy with atebimetinib plus chemotherapy to achieve equal or better outcomes than we see with the triplet therapies [alone]. A global, randomized prospective phase 3 study [expected to launch by the end of 2025] will answer these questions in more clarity.1
References
- Immuneering announces extraordinary 86% overall survival at 9 months in first-line pancreatic cancer patients treated with atebimetinib + mGnP. News release. Immuneering. September 24, 2025. Accessed October 2, 2025. https://ir.immuneering.com/news-releases/news-release-details/immuneering-announces-extraordinary-86-overall-survival-9-months
- Von Hoff DD, Ervin T, Arena FP, et al. Increased survival in pancreatic cancer with nab-paclitaxel plus gemcitabine. N Engl J Med. 2013;369(18):1691-1703. doi:10.1056/NEJMoa1304369
- Conroy T, Desseigne F, Ychou M, et al. FOLFIRINOX versus gemcitabine for metastatic pancreatic cancer. N Engl J Med. 2011;364(19):1817-1825. doi:10.1056/NEJMoa1011923
- Wainberg ZA, Melisi D, Macarulla T, et al. NALIRIFOX versus nab-paclitaxel and gemcitabine in treatment-naive patients with metastatic pancreatic ductal adenocarcinoma (NAPOLI 3): a randomised, open-label, phase 3 trial. Lancet. 2023;402(10409):1272-1281. doi:10.1016/S0140-6736(23)01366-1
- Immuneering announces clinical supply agreement with Regeneron Pharmaceuticals to evaluate IMM-1-104 in combination with Libtayo (cemiplimab). News release. Immuneering. February 6, 2025. Accessed October 2, 2025. https://ir.immuneering.com/news-releases/news-release-details/immuneering-announces-clinical-supply-agreement-regeneron