FDA approval of retifanlimab-dlwr (Zynyz) plus carboplatin/paclitaxel

 for the first-line treatment of patients with inoperable locally recurrent or metastatic squamous cell carcinoma of the anal canal (SCAC) has provided a significant treatment option for this patient population, whose cancer is no longer considered rare, as incidence rates have increased within the past 20 years, according to Cathy Eng, MD, FACP, FASCO.

The regulatory decision was supported by data from the phase 3 POD1UM-303/InterAACT2 trial (NCT04472429), which evaluated retifanlimab plus carboplatin/paclitaxel vs placebo plus carboplatin/paclitaxel in patients with locally recurrent or metastatic SCAC. Of note, the study met its primary end point of progression-free survival (PFS), in which the median PFS was 9.3 months (95% CI, 7.5-11.3) vs 7.4 months (95% CI, 7.1-7.7) in the retifanlimab (n = 154) and placebo (n = 154) arms, respectively (HR, 0.63; 95% CI, 0.47-0.84; 

At the data cutoff date of April 15, 2024, a strong trend of improved overall survival (OS) was demonstrated, although the data were immature.

“[Retifanlimab plus carboplatin/paclitaxel] provides another great opportunity for patients. However, the problem is that we don’t have any other options [after that],” Eng explained during an interview with 

®. “If you move immuno-oncology [IO] therapy from the second line to the frontline, we have no standard of care left in the second-, third-, or fourth-line settings.”

In the interview, Eng discussed the FDA approval of retifanlimab for patients with SCAC, considerations while dissecting data from the 2 respective trials, and how ongoing research is addressing IO drugs moving into the frontline setting.

Eng is the David H. Johnson Endowed Chair in Surgical and Medical Oncology, a professor of medicine in the Department of Hematology and Oncology, and the director for Strategic Relations at the Vanderbilt-Ingram Cancer Center in Nashville, Tennessee. 

: In May, the FDA approved retifanlimab for patients with SCAC. What are the implications of having retifanlimab available for these 2 indications?

: [POD1UM-303] was the first trial to be presented to demonstrate a PFS benefit of a little over 2 months for [patients with] newly diagnosed metastatic SCAC. [Retifanlimab] is a new option [that allows us] to move IO therapy to the frontline setting. Other trials are ongoing. The POD1UM-303 trial was largely conducted overseas, with a very small component of patients [from the United States (US)]. It’s a huge opportunity for pharmaceutical companies to pursue for metastatic SCAC, and there is an ongoing trial, EA2165 [NCT03233711], that we don’t have the results for in regards to IO therapy in the locally advanced, high-risk setting. Everybody’s anxiously awaiting those results because it’s [looking at 6 months of IO therapy in the adjuvant setting in] patients who have completed their chemoradiation therapy but are at high risk of recurrence due to tumors greater than 4 cm or positive nodes.

There’s another trial looking at IO therapy in the earlier stage, chemoradiation therapy setting, from our European colleagues, that is also currently pending. The IO space is moving towards the frontline, and hopefully, we’ll be moving [IO] into the locally advanced setting. We hope the findings from the phase 3 EA2176 trial (NCT04444921) will validate the findings from the POD1UM-303 study because that would demonstrate that we’re [able to] duplicate those [results] in the US patient population.

In the US, the difference between the [POD1UM-303 and EA2176] studies is that the POD1UM-303 study allowed crossover if patients were in the control arm. EA2176, which is the US study, doesn’t allow crossover, because patients already have nivolumab [Opdivo] plus carboplatin available to them, and it was already [added to] the National Comprehensive Cancer Network guidelines. Our primary end point is purely PFS. OS is a secondary end point, [and therefore] crossover wasn’t needed in the US trial.

How does ongoing research address IO moving into the frontline setting and potentially bringing other agents in to help with treatment sequencing decisions?

We are encouraging pharmaceutical companies to continue to support other efforts in either human papillomavirus [HPV]–associated malignancies or metastatic squamous cell carcinoma malignancies in general. Any breakthroughs that are noted in SCAC can be applied to other HPV-associated malignancies, such as cervical cancer, [among others], because [more than 90% of] anal carcinomas are HPV-associated. It’s an unmet need that pharmaceutical companies should consider. They need to recognize this is not just a rare cancer anymore. This has been rising in incidence as long as my career, by a little less than 3% per year. For over 23 years now, we’ve gone from approximately a little over 2000 cases per year to about 11,000 cases per year in the US. Globally, it’s estimated to be between 40,000 and 50,000 cases per year. That’s important to keep in mind; this is an opportunity for drug development, and pharmaceutical companies need to think broader.

Based on this FDA approval, what takeaways would you offer colleagues about the SCAC treatment paradigm and future research directions in this space?

It’s important [to recognize] that, even within the cooperative group ECOG, we conducted 3 phase 3 trials within the past decade for this patient population. What it demonstrates is that this [research] can be done. The issue is that most of these patients have diffuse metastatic disease. They’re not necessarily cured. We need new treatment options for patients. If we’re prolonging their OS, we will be able to provide them other treatment options down the road. There are so many more unique pathways we need to consider for this patient population. IO resistance is always an issue—it’s very important to keep in mind that these trials only provide systemic chemotherapy. The [POD1UM-303 and EA2176 ]trials only provide systemic chemotherapy for 6 months at a maximum, with the IO therapy, but then the IO therapy is continued for a duration of up to 2 years in both trials.

FDA approves retifanlimab-dlwr with carboplatin and paclitaxel and as a single agent for squamous cell carcinoma of the anal canal. FDA. May 15, 2025. Accessed June 11, 2025. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-retifanlimab-dlwr-carboplatin-and-paclitaxel-and-single-agent-squamous-cell-carcinoma

Rao S, Samalin-Scalzi E, Evesque L, et al. POD1UM-303/InterAACT 2: phase III study of retifanlimab with carboplatin-paclitaxel (c-p) in patients (pts) with inoperable locally recurrent or metastatic squamous cell carcinoma of the anal canal (SCAC) not previously treated with systemic chemotherapy (chemo). 

2024;35(suppl 2):S1217. doi:10.1016/j.annonc.2024.08.2262

Articles

The FDA's approval of retifanlimab-dlwr combined with carboplatin/paclitaxel for first-line treatment of inoperable locally recurrent or metastatic squamous cell carcinoma of the anal canal (SCAC) marks a significant advancement. The decision was based on the phase 3 POD1UM-303/InterAACT2 trial, which showed improved progression-free survival. However, the lack of subsequent treatment options remains a challenge. Ongoing research aims to move immuno-oncology therapies to the frontline setting and explore their potential in other HPV-associated malignancies, addressing the rising incidence of SCAC and unmet treatment needs.

Cathy Eng, MD, FACP, FASCO, highlights the significance of the FDA approval of retifanlimab for managing locally recurrent or metastatic SCAC.

Retifanlimab Presents a New Treatment Option for Locally Recurrent or Metastatic SCAC

Although Merkel cell carcinoma (MCC) remains an aggressive form of skin cancer associated with treatment challenges to treatment, the development of immunotherapy approaches and increased multidisciplinary collaboration have improved the management of this malignancy, according to Michael K. Wong, MD, PhD, FRCPC.

“MCC is an area that is ripe for research, and it’s one of opportunity for great outcomes for our patients,” Wong said in an interview with 

®. “When possible, it’s better to [consider] immunotherapy as a frontline therapy because in all the clinical trials of immunotherapy in MCC, the [overall] response rate [ORR] has been highest in the frontline. In the second- or third-line of therapy, it’s effective but the ORR is lessened. [However], there are a variety of [situations] where that may not be the case, and that’s why having a total assessment by [a multidisciplinary] team is important for our patients with MCC.”

Wong is a physician in chief and professor of oncology in the Department of Medicine at Roswell Park Comprehensive Cancer Center in Buffalo, New York.

Retifanlimab-dlwr (Zynyz) became an approved immunotherapy option for patients with MCC when, 

in March 2023, the FDA granted accelerated approval to the agent

 for the treatment of adult patients with metastatic or recurrent locally advanced MCC. The regulatory decision was supported by data from the single-arm phase 2 PODIUM-201 study (NCT03599713), which demonstrated that patients with chemotherapy-naive metastatic or recurrent locally advanced MCC who received retifanlimab (n = 65) achieved an objective response rate of 52% (95% CI, 40%-65%), including a complete response rate of 18%. Notably, 76% of responders experienced a duration of response (DOR) of at least 6 months, and 62% had a DOR of at least 12 months.

In the interview, Wong discussed the historical challenges associated with treating patients with MCC, the importance of multidisciplinary management of the disease, and the impact of the emergence of immunotherapies such as retifanlimab in the space.

: What have been some of the treatment challenges for patients with MCC?

: MCC is one of the most aggressive skin cancers we know of, and it has a very high mitotic rate. It has a reputation for extensive metastatic ability. In the past, this was a disease that was difficult to treat; it was treated with cytotoxic chemotherapy and radiation. [However], there have been tremendous changes in the management of MCC, to the point where we now have the routine expectation of response, and we see long-term survivors of this disease.

An important [aspect] of MCC is that it’s a lesion that can creep up on individuals. It’s not pigmented, so it’s not like a mole where one can see a change. In fact, if you survey patients with a diagnosis of MCC as to what they were told in the beginning, you get [responses about the disease looking like] a cyst or a bug bite, so it’s difficult to detect. However, the key is, as an adult, if you notice any changes in your body in a significant way that are persistent and unrelenting, then it’s time to seek medical attention. We know that MCC is a lesion that grows because of how mitotic it is. It grows, begins to change, and becomes symptomatic. If you start having symptoms, that’s a red flag to seek medical attention.

There are certain situations in which MCC can be more prominent. We know that it occurs in a population that, on average, is [approximately] 10 years older than the average melanoma population. We know there’s a propensity for it to occur in individuals with an immunologic issue, either from pre-existing disease or long-term immunosuppression.

What is important to know about identifying MCC and differentiating it from other forms of skin cancer?

MCC is considered a rare tumor, [but] we are finding that the incidence is going up in [the United States, which] reflects the fact that we are better at recognizing it. [This is] because we are learning more about it, and patients and physicians are paying attention to this rare cancer. Importantly, on the side of diagnosis, there are new tools and ways of interrogating tissue to make a diagnosis.

The incidence [rate] used to be [approximately] 1 per 1 million [individuals], but MCC is becoming more prevalent as we are [better] understanding the disease. Whenever there’s [a lesion] and there’s doubt as to what it is, the next step is to do a biopsy. MCC is distinctive under the microscope; it looks very different than melanoma, squamous cell carcinoma, or basal cell carcinoma. Once you have a [sample] under the microscope, the diagnosis comes to the forefront quickly.

How can a multidisciplinary care be used for the management of MCC?

The key to successful treatment of MCC is a multidisciplinary approach, which means that you want to engage the surgeon, radiation oncologist, and medical oncologist. The reason for that is that is this disease is best handled in a way that involves all 3 specialties. I tell patients that one of the most important individuals involved in their care is the pathologist, who is someone they never see.

Upon the discovery of the disease, the patient undergoes a thorough physical examination to ensure that we understand exactly what’s going on. We want to make sure that we know the location [of the disease] and that there isn’t any obvious clinical spread. Depending on the what the physician sees, they may order further imaging, such as a CT scan.

If the disease is localized, the treatment requires a surgeon to remove the tumor. We know that a biopsy and [tumor resection] is not good enough; [the patient] needs to have a proper excision. That’s important because MCC tumors have a reputation for being more than you see. Whenever we see MCC on the skin, it’s a bit like an iceberg, and you worry about the part you don’t see.

The analysis under the microscope tells you whether you need a complete resection. Oftentimes, patients will say, ‘Did the doctor get it all?’ Knowing that requires the pathologist to declare the margins are free. We [also] know that there are certain features under the microscope associated with spread beyond the primary site, which includes depth of invasion and involvement of other critical structures deep in the skin.

If [a patient] checks those boxes, then a surgeon may sample the lymph nodes associated with that site. Sometimes surgeons will map out [the surrounding] lymph nodes and take samples to ensure the disease hasn’t spread. We determine [when to do that] by looking at the [sample] under the microscope and the physical examination.

All of this comes back to the importance of a multidisciplinary approach. What we see from the resection and whether the lymph nodes are positive [determine] whether we need radiation. [Radiation is sometimes needed] to sterilize the area around the tumor so that we get rid of [the disease] once and for all. Luckily, MCC is one of those tumors which are particularly sensitive to radiation, so it’s a good modality to use.

I’m a medical oncologist, and, in the past, we didn’t get too involved because there weren’t a lot of [treatment] options, but there’s been tremendous change in the field, and that has to do with the recognition that this tumor is sensitive to immunotherapy. That has been a real breakthrough in this area. It turns out that MCC is a cancer that can evoke an immune response in the body. By using immunotherapy, you can unleash the patient’s immune system to attack the cancer. That has been a revolutionary change in the treatment of MCC.

How has the FDA approval of retifanlimab and the development of other immunotherapies affected the treatment paradigm of MCC?

Retifanlimabi s an immunotherapy, and it [adds to the] line of known immunotherapies that can attack the cancer. The current way we treat MCC—whether it’s locally advanced locally or metastatic—is to use medicines that will trigger the immune system to fight the cancer. These medicines target PD-L1.

There are now several [agents] that are used in MCC. Useful [agents include] avelumab [Bavencio], pembrolizumab [Keyrtuda], nivolumab [Opdivo], and retifanlimab. These are very effective immunotherapies. The use of immunotherapies in MCC comes with some of the highest response rates in oncology, approaching 50% to 60%. These responses can occur quickly, and within 1 to 3 infusions you can know whether you’ve triggered [a response].

The use of immunotherapy is global in a sense that it will attack the cancer anywhere in your body. Patients with extensive disease can respond to immunotherapy dramatically, and that has been the real key in in the change of how we treat this cancer. The advantage of immunotherapy is that it’s a bit like the gift that keeps on giving. It is intrinsic to the patient, and you’re triggering something within that patient. At some point, we can allow the patient’s immune system to take over, and we don’t need to treat them forever. With these robust responses, the door opens for a cure, and we are able to have long-term results in the absence of having to give [continuous] therapy. This has truly revolutionized [the treatment of] this disease.

Is there any other ongoing research in the field that could help move the needle for treatment?

The recognition that immunotherapy works in MCC has been a [key] breakthrough. It means that all the research in immunotherapy and all of those concepts we have in other cancers become applicable to MCC. We’re interested in using other checkpoint inhibitors, [such as] the addition of an antibody to an anti–CTLA-4 [agent] or an anti-LAG3 [agent]. Those are strategies have found use in other cancers, in particular melanoma. Their use is now being pioneered in MCC.

We [also] have recognized that vaccine therapies may be important. We now have intratumor oncolytic vaccines, where you can inject a vaccine directly into the tumor to induce an immune response. Something which is unique to MCC and not found in any other cancer is a recognition that there may be a viral link-up. The Merkel cell polyomavirus is found ubiquitously and for reasons we don’t understand it can integrate into the skin and cause MCC.

This is all new [research], but something that’s come as an offshoot of the recognition that we could use molecules that attack specific pathways within the Merkel polyomavirus to affect a response in the tumor. [This is] an exciting area which is growing. We don’t know where it’s going to go, but there’s a hint of efficacy. It’s something unique to MCC that is not found in any other cancer.

Finally, there’s a recognition that we have barely begun to scratch the surface of this disease. We are finding more ways to attack it, and it’s an area of prolific interest and research. I’m certain that there’s more to come in a short time.

FDA grants accelerated approval to retifanlimab-dlwr for metastatic or recurrent locally advanced Merkel cell carcinoma. FDA. March 22, 2023. Accessed May 14, 2025. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-retifanlimab-dlwr-metastatic-or-recurrent-locally-advanced-merkel

Michael K. Wong, MD, PhD, FRCPC, discusses the landscape of Merkel cell carcinoma, including the role of immunotherapy and multidisciplinary treatment.

Multidisciplinary Collaboration and Immunotherapy Help Overcome Treatment Challenges in MCC

With the 2023 FDA approval of retifanlimab-dlwr (Zynyz), which was supported by data from the phase 2 POD1UM-201 trial (NCT03599713), patients with Merkel cell carcinoma (MCC) gained a safe and effective treatment option with response durability and quality of life advantages compared with traditional chemotherapy-based approaches, according to Shailender Bhatia, MD.

“It’s nice to have multiple options available for our patients; there was a time in MCC [when] the only agent that we had access to outside of clinical trials was cytotoxic chemotherapy,” Bhatia said in an interview with 

®. “[Historically], chemotherapy has a very high response rate in patients with metastatic MCC, to the tune of [approximately] 60% in some retrospective series. [Unfortunately], those responses were not very durable. The median progression-free survival [PFS] in patients with chemotherapy was only [approximately] 3 to 4 months at best.”

Bhatia is a professor in the Clinical Research Division at Fred Hutch Cancer Center and a professor in the Division of Hematology and Oncology at the University of Washington, both in Seattle.

Retifanlimab is an IgG4 monoclonal antibody that targets PD-1.

agent received accelerated approval from the FDA in March 2023

 for the treatment of adult patients with metastatic or recurrent locally advanced MCC.

 Updated data from POD1UM-201 presented during the 2023 European Society for Medical Oncology Congress demonstrated that the agent had clinically meaningful activity in chemotherapy-naive patients with advanced or metastatic MCC with a manageable safety profile.

At the March 10, 2023, data cutoff, patients who received retifanlimab (n = 101) achieved an objective response rate (ORR) of 53.5% (95% CI, 43.3%-63.5%), including a complete response rate of 16.8%. At a median follow-up of 17.6 months (range, 1.1-38.7), the median duration of response (DOR) was 25.3 months (95% CI, 14.2-not estimable [NE]). The 6-, 12-, and 24-month DOR rates were 82% (95% CI, 68%-90%), 71% (95% CI, 57%-82%), and 56% (95% CI, 39%-69%), respectively. The disease control rate (DCR) was 59.4%.

“These responses were very durable,” Bhatia noted. “Many of these patients have continued to maintain their responses in my clinic. The response rates with retifanlimab and other [similar] agents are in the same range as chemotherapy, but the differentiating factor is that these responses are very durable.”

The median overall survival (OS) was not reached (95% CI, NE-NE) and the median PFS was 12.7 months (95% CI, 7.3-24.9). Data from a subgroup analysis revealed that retifanlimab was active across subgroups with the highest ORRs being reported in patients who were not White (n = 23; 69.6% [95% CI, 47.1%-86.8%]), those who were Hispanic or Latino (n = 26; 61.5% [95% CI, 40.6%-79.8%]), and those with advanced stage disease (n = 10; 60.0% [95% CI, 26.2%-87.8%]).

Patients who were positive for the MCC polyomavirus with a PD-L1 tumor proportion score (TPS) of less than 1% (n = 57) achieved an ORR of 43.9% (95% CI, 30.7%-57.6%); patients with a PD-L1 TPS of at least 1% (n = 15) experienced an ORR of 86.7% (95% CI, 59.5%-98.3%). These respective rates among patients who were MCC polyomavirus negative were 43.8% (95% CI, 19.8%-70.1%; n = 7/16) and 75.0% (95% CI, 19.4%-99.4%; n = 3/4).

In terms of safety, any-grade treatment-emergent adverse effects (TEAEs) were reported in 91.1% of patients. Any-grade treatment-related TEAEs (66.3%), grade 3 or higher TEAEs (31.7%), grade 3 or higher treatment-related TEAEs (16.8%), any-grade serious TEAEs (25.7%), and any-grade serious treatment-related TEAEs (11.9%) also occurred. TEAEs leading to treatment discontinuation or death occurred at rates of 20.8% and 4.0%, respectively.

Any-grade and grade 3 or higher immune-related TEAEs were reported in 34.7% and 10.9% of patients, respectively. Any-grade immune-related adverse effects (irAEs) included skin reaction (9.9%), hypothyroidism (7.9%), and hyperthyroidism (5.9%). Grade 3 or higher irAEs consisted of skin reaction (2.0%), pneumonitis (2.0%), and adrenal insufficiency (1.0%).

“The safety profile of retifanlimab is similar to other drugs in this class, [such as] pembrolizumab [Keytruda], avelumab [Bavencio], and nivolumab [Opdivo],” Bhatia said. “MCC is generally considered to be a disease of more elderly [patients], and now we have great data [showing] that these immune checkpoint inhibitors, specifically PD-1/PD-L1 blocking monotherapy agents have very good safety and tolerability, even in an elderly population.”

POD1UM-201 was an open-label, single-arm, multicenter trial that enrolled adult patients with MCC with distant metastatic disease or recurrent, advanced locoregional disease who were not amenable to surgery or radiation.

 Eligible patients also needed to have measurable disease per RECIST 1.1 criteria, an ECOG performance status of 0 or 1, and available tumor tissue for central pathology review.

The study initially included arms for chemotherapy-refractory and -naive patients; enrollment was limited to chemotherapy-naive patients per an April 9, 2020, protocol amendment.

 All patients received 500 mg of intravenous retifanlimab over 60 minutes every 4 weeks on day 1 of each 28-day cycle. Treatment continued for up to 2 years or until disease progression, intolerable toxicity, patient withdrawal, loss to follow-up, death, or premature discontinuation for any other reason.

“Since the majority of the patients have responses [to retifanlimab] we had the happy problem of people continuing on treatment for a long time,” Bhatia explained. “As they continue treatment, the logistics start becoming a problem when patients have to come in every 2 or 3 weeks [with other agents]. After a while, it starts adding to the burden of care, not only on the provider side, but also the patient side. Our interest in exploring retifanlimab as an alternative agent was mostly driven by the reduced frequency of every 4 weeks.”

The primary end point was ORR per RECIST 1.1 criteria per independent central radiographic review.

 Secondary end points included DOR, DCR, PFS, OS, and safety. As of June 28, 2024, POD1UM-201 is completed.

“Retifanlimab appears to be similarly effective [compared with] other agents and, over time, the reduced frequency benefits start to add up,” Bhatia said. “If you look at many phase 1 trials of novel immunotherapies that are being tested, MCC is an outlier in terms of how it responds to those [agents]. [Although] it’s a severe cancer, there are certainly great opportunities to keep testing immunotherapies in this [disease].”

Diagnosis of MCC with distant metastatic disease or recurrent, advanced locoregional disease not amenable to surgery or radiation

Availability of tumor tissue (fresh or archival) for central pathology review

Willingness to avoid pregnancy or fathering children based on protocol-defined criteria

IV retifanlimab 500 mg once every 4 weeks

AUC0-t, area under the plasma concentration-time curve from time zero to time t; Cmax, maximum observed plasma concentration; Cmin, minimum observed plasma concentration over the dose interval; DCR, disease control rate; DOR, duration of response; ICR, independent central radiographic review; MCC, Merkel cell carcinoma; ORR, overall response rate; OS, overall survival; PFS, progression-free survival; TEAE, treatment-emergent adverse effect.

Grignani G, Rutkowski P, Lebbe C, et al. Updated results from POD1UM-201: a phase II study of retifanlimab in patients with advanced or metastatic Merkel cell carcinoma (MCC). 

. 2023;34(suppl 2):S686. doi:10.1016/j.annonc.2023.09.2280

FDA grants accelerated approval to retifanlimab-dlwr for metastatic or recurrent locally advanced Merkel cell carcinoma. FDA. March 22, 2023. Accessed March 10, 2025. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-retifanlimab-dlwr-metastatic-or-recurrent-locally-advanced-merkel

A study of INCMGA00012 in metastatic Merkel cell carcinoma (POD1UM-201). ClinicalTrials.gov. Updated October 15, 2024. Accessed March 10, 2025. https://clinicaltrials.gov/study/NCT03599713

The FDA's 2023 approval of retifanlimab-dlwr (Zynyz) offers a promising treatment for Merkel cell carcinoma (MCC), demonstrating durable responses and improved quality of life over traditional chemotherapy. Retifanlimab, a PD-1 targeting monoclonal antibody, showed significant efficacy in the phase 2 POD1UM-201 trial, with a 53.5% objective response rate and a median duration of response of 25.3 months. The safety profile is comparable to other PD-1/PD-L1 inhibitors, making it a viable option for elderly patients. The trial highlighted retifanlimab's effectiveness across diverse patient subgroups.

Retifanlimab demonstrated durable activity with a tolerable safety profile in patients with chemotherapy-naive MCC.

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Retifanlimab Presents a New Treatment Option for Locally Recurrent or Metastatic SCAC

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