New developments in the biology and the treatment of metastatic Merkel cell carcinoma

S2k Guideline - Merkel cell carcinoma (MCC, neuroendocrine carcinoma of the skin) - Update 2022

Merkel cell carcinoma (MCC, ICD-O M8247/3) is a rare, malignant, primary skin tumor with epithelial and neuroendocrine differentiation. The tumor cells share many morphologic, immunohistochemical, and ultrastructural features with cutaneous Merkel cells. Nevertheless, the cell of origin of MCC is unclear. MCC appears clinically as a reddish to purple spherical tumor with a smooth, shiny surface and a soft to turgid, elastic consistency, usually showing rapid growth. Spontaneous and often complete regressions of the tumor are observed. These likely immunologically-mediated regressions explain the cases in which only lymph node or distant metastases are found at the time of initial diagnosis and why the tumor responds very well to immunomodulatory therapies even at advanced stages. Due to its aggressiveness, the usually given indication for sentinel lymph node biopsy, the indication of adjuvant therapies to be evaluated, as well as the complexity of the necessary diagnostics, clinical management should already be determined by an interdisciplinary tumor board at the time of initial diagnosis.

Diagnosis and treatment of Merkel cell carcinoma: European consensus-based interdisciplinary guideline - Update 2022

Merkel cell carcinoma (MCC) is a rare skin cancer, accounting for less than 1% of all cutaneous malignancies. It is found predominantly in white populations and risk factors include advanced age, ultraviolet exposure, male sex, immunosuppression, such as AIDS/HIV infection, haematological malignancies or solid organ transplantation, and Merkel cell polyomavirus infection. MCC is an aggressive tumour with 26% of cases presenting lymph node involvement at diagnosis and 8% with distant metastases. Five-year overall survival rates range between 48% and 63%. Two subsets of MCC have been characterised with distinct molecular pathogenetic pathways: ultraviolet-induced MCC versus virus-positive MCC, which carries a better prognosis. In both subtypes, there are alterations in the retinoblastoma protein and p53 gene structure and function. MCC typically manifests as a red nodule or plaque with fast growth, most commonly on sun exposed areas. Histopathology (small-cell neuroendocrine appearance) and immunohistochemistry (CK20 positivity and TTF-1 negativity) confirm the diagnosis. The current staging systems are the American Joint Committee on Cancer/Union for international Cancer control 8th edition. Baseline whole body imaging is encouraged to rule out regional and distant metastasis. For localised MCC, first-line treatment is surgical excision with postoperative margin assessment followed by adjuvant radiation therapy (RT). Sentinel lymph node biopsy is recommended in all patients with MCC without clinically detectable lymph nodes or distant metastasis. Adjuvant RT alone, eventually combined with complete lymph nodes dissection is proposed in case of micrometastatic nodal involvement. In case of macroscopic nodal involvement, the standard of care is complete lymph nodes dissection potentially followed by post-operative RT. Immunotherapy with anti-PD-(L)1 antibodies should be offered as first-line systemic treatment in advanced MCC. Chemotherapy can be used when patients fail to respond or are intolerant for anti-PD-(L)1 immunotherapy or clinical trials.

Merkel cell polyomavirus and associated Merkel cell carcinoma

Merkel cell polyomavirus (MCPyV) is a ubiquitous skin infection that can cause Merkel cell carcinoma (MCC), a highly lethal form of skin cancer with a nearly 50% mortality rate. Since the discovery of MCPyV in 2008, great advances have been made to improve our understanding of how the viral encoded oncoproteins contribute to MCC oncogenesis. However, our knowledge of the MCPyV infectious life cycle and its oncogenic mechanisms are still incomplete. The incidence of MCC has tripled over the past two decades, but effective treatments are lacking. Only recently have there been major victories in combatting metastatic MCC with the application of PD-1 immune checkpoint blockade. Still, these immune-based therapies are not ideal for patients with a medical need to maintain systemic immune suppression. As such, a better understanding of MCPyV's oncogenic mechanisms is needed in order to develop more effective and targeted therapies against virus-associated MCC. In this review, we discuss current areas of interest for MCPyV and MCC research and the progress made in elucidating both the natural host of MCPyV infection and the cell of origin for MCC. We also highlight the remaining gaps in our knowledge on the transcriptional regulation of MCPyV, which may be key to understanding and targeting viral oncogenesis for developing future therapies.

The Role of Histone Post-Translational Modifications in Merkel Cell Carcinoma

Merkel Cell Carcinoma (MCC) is a rare but highly aggressive form of non–melanoma skin cancer whose 5-year survival rate is 63%. Merkel cell polyomavirus (MCPyV), a small DNA tumor virus, is the etiological agent of MCC. Although representing a small proportion of MCC cases, MCPyV-negative MCCs have also been identified. The role of epigenetic mechanisms, including histone post-translational modifications (PTMs) in MCC, have been only partially determined. This review aims to describe the most recent progress on PTMs and their regulative factors in the context of MCC onset/development, providing an overview of current findings on both MCC subtypes. An outline of current knowledge on the potential employment of PTMs and related factors as diagnostic and prognostic markers, as well as novel treatment strategies targeting the reversibility of PTMs for MCC therapy is provided. Recent research shows that PTMs are emerging as important epigenetic players involved in MCC onset/development, and therefore may show a potential clinical significance. Deeper and integrated knowledge of currently known PTM dysregulations is of paramount importance in order to understand the molecular basis of MCC and improve the diagnosis, prognosis, and therapeutic options for this deadly tumor.

The treatment of Merkel cell carcinoma with immune checkpoint inhibitors: implications for patients with rheumatoid arthritis

Objectives

Merkel cell carcinoma (MCC) is a rare, highly aggressive neuroendocrine skin cancer, which typically affects elderly and immunocompromised and/or immunosuppressed patients. The checkpoint inhibitor avelumab, a mAb targeting the anti-programmed cell death ligand 1 (anti-PD-L1), has revolutionized the treatment of metastatic MCC, achieving dramatic improvements in disease control and overall survival. However, checkpoint inhibitors are associated with the development of immune-related adverse events, such as exacerbation of pre-existing RA. Although most immune-related adverse events can be managed successfully with CSs, their frequent and/or long-term use runs the risk of undermining the efficacy of immune checkpoint inhibition.

Methods

We report two cases of MCC, in which immunosuppressive therapy for the management of RA was administered.

Results

Immunosuppression for (i) pre-existing and (ii) immune checkpoint inhibitor-exacerbated RA was associated with progression of metastatic MCC.

Conclusion

Any decision to initiate immunosuppressive treatment for RA in patients receiving immune checkpoint inhibitor therapy should include careful consideration of the risk of potentially fatal cancer progression and be taken after consultation with the patient’s oncologist and rheumatologist. When the immunosuppressive treatment is required, it should be administered for as short a time as possible and under strict clinical and radiological surveillance.

Merkel Cell Polyomavirus and Human Merkel Cell Carcinoma

Merkel cell polyomavirus (MCPyV) is the most recently discovered human oncogenic virus. MCPyV asymptomatically infects most of the human population. In the elderly and immunocompromised, however, it can cause a highly lethal form of human skin cancer called Merkel cell carcinoma (MCC). Distinct from the productive MCPyV infection that replicates the viral genome as episomes, MCC tumors contain replication-incompetent, integrated viral genomes. Mutant MCPyV tumor antigen genes expressed from the integrated viral genomes are essential for driving the oncogenic development of MCPyV-associated MCC. In this chapter, we summarize recent discoveries on MCPyV virology, mechanisms of MCPyV-mediated oncogenesis, and the current therapeutic strategies for MCPyV-associated MCCs.

Selective reactivation of STING signaling to target Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a lethal skin cancer that metastasizes rapidly. Few effective treatments are available for patients with metastatic MCC. Poor intratumoral T cell infiltration and activation are major barriers that prevent MCC eradication by the immune system. However, the mechanisms that drive the immunologically restrictive tumor microenvironment remain poorly understood. In this study, we discovered that the innate immune regulator stimulator of IFN genes (STING) is completely silenced in MCCs. To reactivate STING in MCC, we developed an application of a human STING mutant, STING^{S162A/G230I/Q266I}, which we found to be readily stimulated by a mouse STING agonist, DMXAA. This STING molecule was efficiently delivered to MCC cells via an AAV vector. Introducing STING^{S162A/G230I/Q266I} expression and stimulating its activity by DMXAA in MCC cells reactivates their antitumor inflammatory cytokine/chemokine production. In response to MCC cells with restored STING, cocultured T cells expressing MCPyV-specific T cell receptors (TCRs) show increased cytokine production, migration toward tumor cells, and tumor cell killing. Our study therefore suggests that STING deficiency contributes to the immune suppressive nature of MCCs. More importantly, DMXAA stimulation of STING^{S162A/G230I/Q266I} causes robust cell death in MCCs as well as several other STING-silenced cancers. Because tumor antigens and DNA released by dying cancer cells have the potential to amplify innate immune response and activate antitumor adaptive responses, our finding indicates that targeted delivery and activation of STING^{S162A/G230I/Q266I} in tumor cells holds great therapeutic promise for the treatment of MCC and many other STING-deficient cancers.

The Current Landscape of Immune Checkpoint Inhibition for Solid Malignancies

Immunotherapy has led to unprecedented improvement in the treatment and prognosis of high-risk resectable and metastatic disease across cancer types. Nowhere is this better highlighted than in the management of advanced and metastatic melanoma with the introduction of molecularly targeted therapies and immune checkpoint inhibitors. Following their success in melanoma, immunotherapies have also been evaluated and their use approved in the management across a variety of other solid malignancies in the neoadjuvant, adjuvant, and advanced/metastatic setting. This review provides an overview of the current landscape of immune checkpoint inhibition for solid malignancies.

Combining DNA Damage Induction with BCL-2 Inhibition to Enhance Merkel Cell Carcinoma Cytotoxicity

Merkel cell carcinoma (MCC) is a highly lethal skin cancer. MCC tumors rapidly develop resistance to the chemotherapies tested to date. While PD-1/PD-L1 immune checkpoint blockade has demonstrated success in MCC treatment, a significant portion of MCC patients are nonresponsive. Therefore, the pressing need for effective MCC chemotherapies remains. We screened a library of natural products and discovered that one compound, glaucarubin, potently reduced the viability of Merkel cell polyomavirus (MCPyV)-positive MCCs, while remaining nontoxic to primary human fibroblasts and MCPyV-negative MCC cell lines tested. Protein array and Western blot analyses revealed that glaucarubin induces DNA damage and PARP-1 cleavage that correlates with the loss of viability in MCC cells. However, high basal expression of the antiapoptotic factor BCL-2 allowed a subpopulation of cells to survive glaucarubin treatment. Previous studies have shown that, while targeting BCL-2 family proteins significantly decreases MCC cell viability, BCL-2 antisense therapy alone was insufficient to inhibit tumor growth in patients with advanced MCC. We discovered that treatment with an FDA-approved BCL-2 inhibitor in the context of glaucarubin-induced DNA damage led to near complete killing in multiple MCPyV-positive MCC cell lines that express high levels of BCL-2. The combination of DNA damage-induced apoptosis and BCL-2 inhibition thus represents a novel therapeutic strategy for MCPyV-positive MCCs.

[Immune checkpoint inhibition in Merkel cell carcinoma]

BACKGROUND

Merkel cell carcinoma (MCC) is a rare but aggressive form of skin cancer in which Merkel cell polyomavirus infection and chronic exposure to ultraviolet radiation are key risk factors. Immune checkpoint inhibition has revolutionized the treatment of locally advanced, inoperable and metastatic MCC.

AIM

To outline the modern management of MCC based on advances in our understanding of MCC tumour biology and the development of immune checkpoint inhibitors, namely inhibitors of programmed cell death protein (PD)-1- and PD‑1 ligand 1 (PD-L1).

METHODS

A review of the scientific literature listed in PubMed.

RESULTS

First line therapy with the PD-L1 blocking antibody avelumab is associated with a response rate of 62%. In the second line setting, for example after chemotherapy, the response rate only reaches 33%. However, in patients who responded in the second line setting, 69% remained relapse free after 2 years. Treatment responses occurred on average after 6.1 weeks of therapy. First line treatment with pembrolizumab (anti-PD‑1 antibody) is associated with a 2-year survival rate of 69% and the median survival rate has not been reached. Whilst the various chemotherapy regimens are associated with similar response rates, these are typically short lived.

DISCUSSION

Checkpoint inhibition offers an effective treatment option for patients with MCC. Avelumab is currently licensed as a treatment for metastatic disease. Chemotherapy remains an option to reduce tumor load, or in the context of resistance and/or contraindications to immune checkpoint therapy. Adjuvant and neoadjuvant use of checkpoint inhibition in MCC may represent a future treatment strategy pending the results of on-going clinical trials.

Diffuse lichen planus-like keratoses and clinical pseudo-progression associated with avelumab treatment for Merkel cell carcinoma, a case report

Background

Avelumab is an anti-programmed cell death ligand 1 (PD-L1) antibody approved for treatment of Merkel cell carcinoma (MCC) and locally advanced or metastatic urothelial carcinoma. It shares a similar side effect profile to other immune checkpoint inhibitors, including immune-related adverse reactions in the skin. These adverse skin reactions can present as a morbilliform exanthem, lichenoid dermatitis, vitiligo, autoimmune bullous disorder, among others.

Case presentation

We describe a patient with advanced MCC successfully treated with avelumab who developed acute onset diffuse lichen planus-like keratoses (LPLK) at sites of existing seborrheic keratoses (SK) and lentigines. Histopathology of an affected SK revealed papillomatous epidermal hyperplasia with lichenoid interface changes, numerous dyskeratotic keratinocytes and intermittent hypergranulosis. The findings resembled lichen planus (LP) arising in an SK. Onset of the skin symptoms corresponded with an inflammatory cancer response (clinical pseudo-progression), and the eruption improved as overall tumor burden decreased. The patient’s pruritus was treated with topical steroids and cyrotherapy for individual symptomatic lesions.

Conclusion

Diffuse LPLK is a distinct immune-related reaction pattern associated with PD-L1/PD-1 checkpoint blockade. This is an important side effect to be aware of as LPLK frequently mimic keratinocytic neoplasms. Further observation is needed to assess the prevalence and significance of this immune therapy-associated adverse reaction.

MHC class-I downregulation in PD-1/PD-L1 inhibitor refractory Merkel cell carcinoma and its potential reversal by histone deacetylase inhibition: a case series

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive skin cancer in which PD-1/PD-L1 blockade has shown remarkable response rates. However, a significant proportion of patients shows primary or secondary resistance against PD-1/PD-L1 inhibition, with HLA class-I downregulation and insufficient influx of CD8+ T cells into the tumor as possible immune escape mechanisms. Histone deacetylase inhibitors (HDACi) have been demonstrated to reverse low HLA class-I expression caused by epigenetic downregulation of the antigen machinery (APM) in vitro and in pre-clinical models in vivo.

CASE PRESENTATIONS

We report four cases of patients with metastatic MCC who did not respond to immunotherapy by PD-1/PD-L1 blockade. Two of the patients received, subsequently, the HDACi panobinostat in combination with PD-1/PD-L1 blockade. Tumor biopsies of the patients were analyzed for cellular and molecular markers of antigen processing and presentation as well as the degree of T-cell infiltration.

RESULTS AND CONCLUSION

Low expression of APM-related genes associated with low HLA class-I surface expression was observed in all MCC patients, progressing on PD-1/PD-L1 blockade. In one evaluable patient, of the two treated with the combination therapy of the HDACi, panobinostat and PD-1/PD-L1 blockade, reintroduction of HLA class-I-related genes, enhanced HLA class-I surface expression, and elevated CD8+ T-cell infiltration into the MCC tumor tissue were observed; however, these changes did not translate into a clinical benefit. Our findings suggest that HDACi may be useful to overcome HLA class-I downregulation as a resistance mechanism against anti-PD-1/PD-L1 antibodies in MCC patients. Prospective clinical trials are needed to evaluate this notion.

S2k guidelines for Merkel cell carcinoma (MCC, neuroendocrine carcinoma of the skin) - update 2018

Merkel cell carcinoma (MCC, ICD-O M8247 / 3) is a rare malignant primary skin tumor with epithelial and neuroendocrine differentiation. The neoplastic cells share many morphological, immunohistochemical and ultrastructural characteristics with Merkel cells of the skin. The diagnosis of MCC is rarely made on clinical grounds. Histological and immunohistochemical studies are usually required to confirm the clinical suspicion. Given the frequent occurrence of occult lymph node metastasis, sentinel lymph node biopsy should be performed once distant metastasis has been ruled out by cross-sectional imaging. Primary tumors without evidence of organ metastases are treated with complete surgical excision with appropriate surgical margins. Radiation therapy should be considered at all stages of the disease. For advanced MCC that is no longer amenable to curative treatment by surgery or radiation therapy, there is currently no established systemic therapy for which an improvement in recurrence-free survival or overall survival has been demonstrated in a prospective randomized trial. However, immunotherapy using PD-1/PD-L1 blockade seems to be superior to chemotherapy. Various factors warrant that further diagnostic and therapeutic interventions be determined by an interdisciplinary tumor board. These factors include the tumor's aggressiveness, the frequent indication for sentinel lymph node biopsy along with the frequent occurrence in the head and neck region, the potential indication for adjuvant radiation therapy as well as the complexity of the required diagnostic workup.

Programmed death receptor Ligand 1 expression in eyelid sebaceous carcinoma: a consecutive case series of 41 patients

PURPOSE

A limited number of therapies are available for patients with metastatic eyelid sebaceous carcinoma (SC). Programmed death receptor Ligand 1 (PD-L1) expression and its clinical significance in sebaceous cell carcinoma are presently unknown. This study aimed to evaluate the expression level of PD-L1 in SC.

METHODS

This single centre, retrospective, and comparative study was conducted at the Ninth People's Hospital between August 1, 2013 and September 1, 2016. Twenty primary, 11 recurrent, and 10 lymph node metastatic eyelid SCs of 41 consecutive patients and paired control eyelid samples were enrolled in the study. Immunohistochemical staining of PD-L1 was performed on slides containing SC embedded in paraffin wax. Patient clinical characteristics and PD-L1 expression related to SC prognostic values were evaluated.

RESULTS

Of the 41 patients with eyelid SCs, 58.5% (24/41) were female, and 41.5% (17/41) were male. A total of 43.9% (18/41) were left-sided, and 56.1% (23/41) were right-sided. A total of 2.4% (1/41) of the SCs were located at the canthus, 51.2% (21/41) were located at the upper eyelid, 41.5% (17/41) were located at the lower eyelids, and 2.4% (1/41) invaded the lacrimal sac. A total of 24.4% of the SCs were metastatic (10/41), 48.8% (20/41) were primary tumours, and 26.8% (11/41) resulted from recurrence. A total of 48.8% (20/41) were moderately graded and 51.2% (21/41) were poorly graded. Programmed death receptor Ligand 1 (PD-L1) positive expression was found in 20 (48.8%) cases. Programmed death receptor Ligand 1 (PD-L1) expression was observed on the tumour cell membrane. Higher expression of PD-L1 was correlated with metastatic cases when compared with primary cases (F = 6.69, p = 0.001). There was a higher expression of PD-L1 in the poorly differentiated group compared with the moderately graded group (57.1% poorly graded versus 45.0% moderately graded).

CONCLUSION AND RELEVANCE

Inhibition of PD-L1 expression may be a therapeutic option for metastatic eyelid SCs, although this hypothesis needs to be tested in future clinical trials.

Unknown primary Merkel cell carcinoma with cutaneous spread

The authors present the case of a woman in the seventh decade of life with medical history of: left nephrectomy for renal tuberculosis and non-Hodgkin's lymphoma treated with chemotherapy (QT) and radiotherapy. She presented with a 2-month history of non-tender, left inguinal lymph node enlargement. Positron Emission Tomography (PET)-CT -scanshowed hypermetabolic inguinal and retroperitoneal lymphadenopathies, no primary tumour. On the second dermatological examination a pink, 2 cm plaque on the anterior left knee was noted. The histopathological analysis revealed Merkel cell carcinoma. The patient underwent two lines of systemic QT, with life-threatening toxicities limiting treatment. Followed overwhelming disease progression with lymphoedema and numerous skin metastases in the left lower limb. The patient received palliative care until death. The rare incidence of such neoplasia and its uncommon clinical presentation justifies reporting this case and highlights the importance of multidisciplinary teams in the management of cancer patients.

Immune checkpoint blockade for Merkel cell carcinoma: actual findings and unanswered questions

PURPOSE

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine carcinoma arising from the skin. We aimed to review and deal with some of the most relevant controversial topics on the correct use of immunotherapy for the treatment of MCC.

METHODS

The primary search was carried out via PubMed, EMBASE, and the Cochrane Library (until 31st May, 2018), while other articles and guidelines were retrieved from related papers or those referenced in these papers. Additionally, we performed an extensive search on ClinicalTrials.gov to gather information on the ongoing clinical trials related to this specific topic.

RESULTS

We performed an up-to-date critical review taking into account the results of both retrospective and prospective published studies evaluating these issues: Are there any predictive criteria of response to immunotherapy? What is the correct place of immunotherapy in the treatment algorithm of MCC? What is the best choice after immunotherapy failure? What to do with patients for whom immunotherapy is not been feasible or contraindicated? How long should immunotherapy be prolonged, and what follow-up should be offered after complete response?

CONCLUSION

The therapeutic landscape of MCC is rapidly evolving: many open issues will probably be resolved, and many other questions are likely to arise in the next few years. The results of ongoing prospective clinical trials and of several other studies on these issues are eagerly awaited.

Merkel Cell Carcinoma of the Head in a Young African Albino Woman with HIV/HTLV-1 Coinfection Associated with Multiple Squamous Cell Carcinomas

Merkel cell carcinoma (MCC) is a rare cutaneous neoplasm of presumed neuroendocrine origin, with aggressive behavior and poor prognosis, that tends to have an increased incidence among elderly Caucasians and immunosuppressed individuals. MCC is either associated with a clonal integration of the Merkel cell polyoma virus into the host genome or with genomic alterations caused by chronic UV exposure. Tumors of either carcinogenesis show epithelial, neuroendocrine, and B-lymphoid lineage markers. HIV-infected African albinos have a higher risk of developing skin cancers, including MCC, in comparison with the general population. We report a case of MCC of the head in a young albino woman with a HIV/HTLV-1 coinfection. The patient also suffered from multiple squamous cell carcinomas of the scalp, face, lip, and ears, suggesting an UV carcinogenesis of MCC. The purpose of this case report is to emphasize the relationship between immunosuppression (HIV/HTLV-1 coinfection, chronic sun exposure, ocular-cutaneous albinism, pregnancy) and MCC. It highlights the importance of early diagnosis, dermatological screening with a risk-stratified surveillance, particularly in immunosuppressed albino patients in sub-Saharan Africa, and multidisciplinary management of this biologically unique cutaneous cancer.

Monoclonal Antibodies for the Treatment of Multiple Myeloma: An Update

The past two decades have seen a revolution in multiple myeloma (MM) therapy with the introduction of several small molecules, mostly orally effective, whose mechanisms are based on proteasome inhibition, histone deacetylase (HDAC) blockade, and immunomodulation. Immunotherapeutic approaches to MM treatment using monoclonal antibodies (mAbs), while long in development, began to reap success with the identification of CD38 and SLAMF7 as suitable targets for development, culminating in the 2015 Food and Drug Administration (FDA) approval of daratumumab and elotuzumab, respectively. This review highlights additional mAbs now in the developmental pipeline. Isatuximab, another anti-CD38 mAb, currently is under study in four phase III trials and may offer certain advantages over daratumumab. Several antibody-drug conjugates (ADCs) in the early stages of development are described, including JNJ-63723283, which has attained FDA breakthrough status for MM. Other mAbs described in this review include denosumab, recently approved for myeloma-associated bone loss, and checkpoint inhibitors, although the future status of the latter combined with immunomodulators has been clouded by unacceptably high death rates that caused the FDA to issue clinical holds on several of these trials. Also highlighted are the therapies based on the B Cell Maturation Antigen (BCMA), another very promising target for anti-myeloma development.

Pharmacological Inhibition of Serine Palmitoyl Transferase and Sphingosine Kinase-1/-2 Inhibits Merkel Cell Carcinoma Cell Proliferation

The majority of Merkel cell carcinoma, a highly aggressive neuroendocrine cancer of the skin, is associated with Merkel cell polyomavirus infection. Polyomavirus binding, internalization, and infection are mediated by glycosphingolipids. Besides receptor function, bioactive sphingolipids are increasingly recognized as potent regulators of several hallmarks of cancer. Merkel cell polyomavirus⁺ and Merkel cell polyomavirus^- cells express serine palmitoyl transferase subunits and sphingosine kinase (SK) 1/2 mRNA. Induced expression of Merkel cell polyomavirus-large tumor antigen in human lung fibroblasts resulted in upregulation of SPTLC1-3 and SK 1/2 expression. Therefore, we exploited pharmacological inhibition of sphingolipid metabolism as an option to interfere with proliferation of Merkel cell polyomavirus⁺ Merkel cell carcinoma cell lines. We used myriocin (a serine palmitoyl transferase antagonist) and two SK inhibitors (SKI-II and ABC294640). In MKL-1 and WaGa cells myriocin decreased cellular ceramide, sphingomyelin, and sphingosine-1-phosphate content. SKI-II increased ceramide species but decreased sphingomyelin and sphingosine-1-phosphate concentrations. Aberrant sphingolipid homeostasis was associated with reduced cell viability, increased necrosis, procaspase-3 and PARP processing, caspase-3 activity, and decreased AKT^S473 phosphorylation. Myriocin and SKI-II decreased tumor size and Ki-67 staining of xenografted MKL-1 and WaGa tumors on the chorioallantoic membrane. Our data suggest that pharmacological inhibition of sphingolipid synthesis could represent a potential therapeutic approach in Merkel cell carcinoma.

Efficacy and Safety of First-line Avelumab Treatment in Patients With Stage IV Metastatic Merkel Cell Carcinoma: A Preplanned Interim Analysis of a Clinical Trial

Importance

Merkel cell carcinoma (MCC) is an aggressive skin cancer that is associated with poor survival outcomes in patients with distant metastatic disease. Results of part A of the JAVELIN Merkel 200 trial (avelumab in patients with Merkel cell carcinoma) showed that avelumab, an anti-programmed cell death ligand 1 (PD-L1) antibody, demonstrated efficacy in second-line or later treatment of patients with metastatic MCC (mMCC).

Objective

To evaluate the efficacy and safety of avelumab as first-line treatment for patients with distant mMCC.

Design, Setting, and Participants

JAVELIN Merkel 200 part B is an international, multicenter, single-arm, open-label clinical trial of first-line avelumab monotherapy. Eligible patients were adults with mMCC who had not received prior systemic treatment for metastatic disease. Patients were not selected for PD-L1 expression or Merkel cell polyomavirus status. Data were collected from April 15, 2016, to March 24, 2017, and enrollment is ongoing.

Interventions

Patients received avelumab, 10 mg/kg, by 1-hour intravenous infusion every 2 weeks until confirmed disease progression, unacceptable toxic effects, or withdrawal occurred.

Main Outcomes and Measures

Tumor status was assessed every 6 weeks and evaluated by independent review committee per Response Evaluation Criteria in Solid Tumors version 1.1. The primary end point was durable response, defined as an objective response with a duration of at least 6 months. Secondary end points include best overall response, duration of response, progression-free survival, safety, and tolerability.

Results

As of March 24, 2017, 39 patients were enrolled (30 men and 9 women; median age, 75 years [range, 47-88 years]), with a median follow-up of 5.1 months (range, 0.3-11.3 months). In a preplanned analysis, efficacy was assessed in 29 patients with at least 3 months of follow-up; the confirmed objective response rate was 62.1% (95% CI, 42.3%-79.3%), with 14 of 18 responses (77.8%) ongoing at the time of analysis. In responding patients, the estimated proportion with duration of response of at least 3 months was 93% (95% CI, 61%-99%); duration of response of at least 6 months, 83% (95% CI, 46%-96%). First-line avelumab treatment was generally well tolerated, and no treatment-related deaths or grade 4 adverse events occurred.

Conclusions and Relevance

High rates of response to first-line avelumab therapy in patients with distant mMCC build on previously reported antitumor activity after second-line or later treatment, and maturing progression-free survival data suggest that responses are durable. These data further support avelumab's approval in the United States and European Union and use as a standard-of-care treatment for mMCC.

Trial Registration

clinicaltrials.gov Identifier: NCT02155647.

Circulating Cell-Free miR-375 as Surrogate Marker of Tumor Burden in Merkel Cell Carcinoma

PURPOSE

Merkel cell carcinoma (MCC) is an aggressive skin cancer with neuroendocrine differentiation. There is an unmet need for MCC-specific blood-based surrogate biomarkers of tumor burden; circulating cell-free miRNA may serve this purpose.

EXPERIMENTAL DESIGN

Expression of miR-375 was quantified in 24 MCC and 23 non-MCC cell lines, 67 MCC and 58 non-MCC tumor tissues, sera of 2 preclinical MCC models, and sera of 109 patients with MCC and 30 healthy controls by nCounter human-v2-miRNA expression or miR-375-specific real-time PCR assays. The patients' sera consisted of two retrospective (discovery and training) and two prospective (validation) cohorts.

RESULTS

miR-375 expression was high in MCC cell lines and tissues compared with non-MCCs. It was readily detected in MCC-conditioned medium and sera of preclinical models bearing MCC xenografts. miR-375 levels were higher in sera from tumor-bearing patients with MCC than in tumor-free patients or healthy controls (P < 0.0005). Moreover, miR-375 serum levels correlated with tumor stage in tumor-bearing (P = 0.037) but not in tumor-free (P = 0.372) patients with MCC. miR-375 serum level showed high diagnostic accuracy to discriminate tumor-bearing and tumor-free patients with MCC as demonstrated by ROC curve analysis in the retrospective cohorts (AUC = 0.954 and 0.800) as well as in the prospective cohorts (AUC = 0.929 and 0.959). miR-375 serum level reflected dynamic changes in tumor burden of patients with MCC during therapeutic interventions.

CONCLUSIONS

Circulating cell-free miR-375 proved as a surrogate marker for tumor burden in MCC without restriction to polyomavirus positivity; it thus appears to be useful for therapy monitoring and the follow-up of patients with MCC.

Avelumab: A Review of Its Application in Metastatic Merkel Cell Carcinoma

OBJECTIVE

To summarize the clinical development of avelumab and its clinical relevance in metastatic Merkel cell carcinoma (MCC).

DATA SOURCES

An English-language literature search using PubMed was performed using the terms avelumab, anti-PD-1, anti-PD-L1, and MCC from January of 1950 to March 2018. Data were also obtained from package inserts, meeting abstracts, and clinical registries.

STUDY SELECTION/DATA EXTRACTION

All relevant published articles of avelumab were reviewed. Clinical trial registries and meeting abstracts were used for information about ongoing trials.

DATA SYNTHESIS

Avelumab is a fully human monoclonal antibody that inhibits programmed death ligand-1, which reverses T-cell exhaustion and induces antitumor responses. Avelumab is safe and effective in previously treated metastatic MCC based on a phase II trial of previously treated patients with objective response rates in 28 of 88 patients, including 10 complete responses and 19 partial responses. Median overall survival (OS) was 12.9 months, and 1-year progression-free survival and OS were 30% and 52%, respectively. Grade 3 treatment-related side effects included lymphopenia (2 patients), serum creatine phosphokinase increase (1 patient), aminotransferase elevation (1 patient), and serum cholesterol increase (1 patient). Relevance to Patient Care and Clinical Practice: This review outlines the pharmacology and clinical trial data for avelumab in metastatic MCC and guides clinicians on avelumab's place in therapy.

CONCLUSIONS

Avelumab is the first Food and Drug Administration-approved medication for metastatic MCC and provides an advantage of durable responses and possibly improved tolerability compared with traditional platinum-based chemotherapy. Clinical trials are under way to expand its utility into the adjuvant and frontline settings.

Management of cutaneous Merkel cell carcinoma

PURPOSE

To report the outcomes of patients with previously untreated cutaneous Merkel cell carcinoma (MCC) managed with curative intent.

MATERIAL AND METHODS

Between December 1984 and August 2015, 59 patients with previously untreated cutaneous MCC were managed with curative intent with surgery and adjuvant radiotherapy (54 patients) or radiotherapy alone (5 patients) at the University of Florida. Primary sites included head and neck (45 patients), extremities (11 patients) and trunk (3 patients). Adjuvant chemotherapy was employed in 14 patients. Patients were staged according to the AJCC staging system: stage I, 25 patients; stage IIA, 7 patients; and, stage III, 27 patients. No patients had distant metastases. Median follow-up for all patients was 3.2 years (range, 0.3-20.9 years). Median follow-up for survivors was 6.7 years (range, 1.6-20.9 years).

RESULTS

The 5-year outcomes were as follows: local control, 91%; regional control, 79%; local-regional control, 77%; disease metastasis-free survival, 60%; cause-specific survival, 53%; and overall survival, 39%. The 5-year outcomes for patients with stage I-IIA versus stage-III disease were the following: local-regional control, 90% versus 57% (p = .0115); distant metastasis-free survival, 78% versus 36% (p = .0002); cause-specific survival, 68% versus 35% (p = .0050); and overall survival, 48% versus 27% (p = .0377). Local-regional recurrences occurred in 12 patients; no patients were successfully salvaged. Severe late complications were observed in four patients.

CONCLUSIONS

Although radiotherapy alone or combined with surgery results in a relatively high likelihood of local-regional control, the majority of recurrences are distant and approximately half of patients are cured. Patients with regional disease at diagnosis have significantly worse outcomes.

Epidemiology, biology and therapy of Merkel cell carcinoma: conclusions from the EU project IMMOMEC

Merkel cell carcinoma (MCC) is a highly aggressive, often lethal neuroendocrine cancer. Its carcinogenesis may be either caused by the clonal integration of the Merkel cell polyomavirus into the host genome or by UV-induced mutations. Notably, virally-encoded oncoproteins and UV-induced mutations affect comparable signaling pathways such as RB restriction of cell cycle progression or p53 inactivation. Despite its low incidence, MCC recently received much attention based on its exquisite immunogenicity and the resulting major success of immune modulating therapies. Here, we summarize current knowledge on epidemiology, biology and therapy of MCC as conclusion of the project 'Immune Modulating strategies for treatment of Merkel Cell Carcinoma', which was funded over a 5-year period by the European Commission to investigate innovative immunotherapies for MCC.

Updated efficacy of avelumab in patients with previously treated metastatic Merkel cell carcinoma after ≥1 year of follow-up: JAVELIN Merkel 200, a phase 2 clinical trial

Background

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer associated with poor survival outcomes in patients with distant metastatic disease (mMCC). In an initial analysis from JAVELIN Merkel 200, a phase 2, prospective, open-label, single-arm trial in mMCC, avelumab—a human anti–programmed death-ligand 1 (PD-L1) monoclonal antibody—showed promising efficacy and a safety profile that was generally manageable and tolerable. Here, we report the efficacy of avelumab after ≥1 year of follow-up in patients with distant mMCC that had progressed following prior chemotherapy for metastatic disease.

Patients and methods

Patients received avelumab 10 mg/kg by 1-h intravenous infusion every 2 weeks until confirmed disease progression, unacceptable toxicity, or withdrawal. The primary endpoint was best overall response. Secondary endpoints included duration of response (DOR), progression-free survival (PFS), and overall survival (OS).

Results

Patients (N = 88) were followed for a minimum of 12 months. The confirmed objective response rate was 33.0% (95% CI, 23.3%-43.8%; complete response: 11.4%). An estimated 74% of responses lasted ≥1 year, and 72.4% of responses were ongoing at data cutoff. Responses were durable, with the median DOR not yet reached (95% CI, 18.0 months-not estimable), and PFS was prolonged; 1-year PFS and OS rates were 30% (95% CI, 21%-41%) and 52% (95% CI, 41%-62%), respectively. Median OS was 12.9 months (95% CI, 7.5-not estimable). Subgroup analyses suggested a higher probability of response in patients receiving fewer prior lines of systemic therapy, with a lower baseline disease burden, and with PD-L1–positive tumors; however, durable responses occurred irrespective of baseline factors, including tumor Merkel cell polyomavirus status.

Conclusions

With longer follow-up, avelumab continues to show durable responses and promising survival outcomes in patients with distant mMCC whose disease had progressed after chemotherapy.

Trial registration

Clinicaltrials.gov identifier: NCT02155647.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare but highly aggressive skin cancer with neuroendocrine features. MCC pathogenesis is associated with either the presence of Merkel cell polyomavirus or chronic exposure to ultraviolet light (UV), which can cause a characteristic pattern of multiple DNA mutations. Notably, in the Northern hemisphere, the majority of MCC cases are of viral aetiology; by contrast, in areas with high UV exposure, UV-mediated carcinogenesis is predominant. The two aetiologies share similar clinical, histopathological and prognostic characteristics. MCC presents with a solitary cutaneous or subcutaneous nodule, most frequently in sun-exposed areas. In fact, UV exposure is probably involved in both viral-mediated and non-viral-mediated carcinogenesis, by contributing to immunosuppression or DNA damage, respectively. Confirmation of diagnosis relies on analyses of histological features and immunological marker expression profiles of the lesion. At primary diagnosis, loco-regional metastases are already present in ∼30% of patients. Excision of the tumour is the first-line therapy; if not feasible, radiotherapy can often effectively control the disease. Chemotherapy was the only alternative in advanced-stage or refractory MCC until several clinical trials demonstrated the efficacy of immune-checkpoint inhibitors.