Safety and efficacy profile of mogamulizumab (Poteligeo) in the treatment of cancers: an update evidence from 14 studies

Preclinical and translational pharmacology of afucosylated anti-CCR8 antibody for depletion of tumour-infiltrating regulatory T cells

BACKGROUND AND PURPOSE

RO7502175 is an afucosylated antibody designed to eliminate C-C motif chemokine receptor 8 (CCR8)+ Treg cells in the tumour microenvironment through enhanced antibody-dependent cellular cytotoxicity (ADCC).

EXPERIMENTAL APPROACH

We report findings from preclinical studies characterizing pharmacology, pharmacokinetics (PK)/pharmacodynamics (PD) and safety profile of RO7502175 and discuss the translational PK/PD approach used to inform first-in-human (FiH) dosing strategy and clinical development in solid tumour indications.

KEY RESULTS

RO7502175 demonstrated selective ADCC against human CCR8+ Treg cells from dissociated tumours in vitro. In cynomolgus monkeys, RO7502175 exhibited a biphasic concentration-time profile consistent with immunoglobulin G1 (IgG1) antibodies, reduced CCR8+ Treg cells in the blood, induced minimal and transient cytokine secretion, and was well tolerated with a no-observed-adverse-effect level (NOAEL) of 100 mg·kg-1. Moreover, RO7502175 caused minimal cytokine release from peripheral blood mononuclear cells (PBMCs) in vitro. A quantitative model was developed to capture surrogate anti-murine CCR8 antibody PK/PD and tumour dynamics in mice and RO7502175 PK/PD in cynomolgus monkeys. Subsequently, the model was used to project RO7502175 human PK and receptor occupancy (RO) in patients. Because traditional approaches resulted in a low FiH dose for this molecule, even with its superior preclinical safety profile, an integrated approach based on the totality of preclinical data and modelling insights was used for starting dose selection.

CONCLUSION AND IMPLICATIONS

This work demonstrates a translational research strategy for collecting and utilizing relevant nonclinical data, developing a mechanistic PK/PD model and using a comprehensive approach to inform clinical study design for RO7502175.

Allogeneic hematopoietic stem cell transplantation after mogamulizumab in T-cell lymphoma patients: a retrospective analysis

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important therapy for patients with T-cell lymphomas, including cutaneous T-cell lymphoma (CTCL), adult T-cell lymphoma (ATL), and peripheral T-cell lymphoma (PTCL). Mogamulizumab is an anti-CCR4 antibody that has been associated with an increased risk of transplant-related complications in retrospective analyses of ATL, particularly when administered within 50 days before transplantation. This post hoc analysis of 3 clinical trials examined safety and outcome data for 32 patients with CTCL (n = 23), ATL (n = 7), or PTCL (n = 2) who underwent allo-HSCT after mogamulizumab treatment. Overall, 22 patients (69%) were known to have graft-versus-host disease (GVHD), 8 patients (25%) did not report GVHD, and 2 patients (6%) had unknown GVHD status. Fourteen patients with known GVHD underwent transplantation between 50 and 365 days after their last dose of mogamulizumab, while 2 underwent transplantation within 50 days after treatment. Based on this limited evidence, GVHD was not associated with the time interval from last mogamulizumab dose to transplantation.

Clinical and Real-World Effectiveness of Mogamulizumab: A Narrative Review

Mogamulizumab (MOG) is an antibody targeting the CCR4 receptor, authorized for relapsed or refractory peripheral T-cell (PTCL) and cutaneous T-cell lymphomas (CTCL). Its adoption in guidelines and endorsement by FDA and EMA established it as a systemic treatment, especially for advanced disease stages due to its comparatively lower toxicity. Clinical trials and real-world evidence have underscored its efficacy in advanced CTCLs, including mycosis fungoides and Sézary syndrome; PTCLs; and adult T-cell leukemia/lymphoma (ATLL), showcasing positive outcomes. Notably, the drug has demonstrated significant response rates, disease stability, and extended periods of progression-free survival, suggesting its applicability in cases with multiple treatment lines. Its safety profile is generally manageable, with adverse events (AEs) primarily related to the skin, infusion-related reactions, drug eruptions, autoimmune diseases, and skin disorders. The latter seem to appear as CCR4 can promote the skin-specific homing of lymphocytes, and MOG is directed against this receptor. While combination with immunostimulatory agents like interferon alpha and interleukin 12 has shown promising results, caution is urged when combining with PD1 inhibitors due to the heightened risk of immune-mediated AEs. The introduction of MOG as a systemic treatment implies a significant advancement in managing these diseases, supported by its favorable safety profile and complementary mechanisms.

Clinicopathological definition, management and prognostic value of mogamulizumab-associated rash and other cutaneous events: A systematic review

Mogamulizumab is a first-in-class IgG1k monoclonal antibody that selectively targets the chemokine receptor type 4. The drug has received Food and Drug administration authorisation for mycosis fungoides and Sézary syndrome following failure of at least one previous course of systemic therapy and now is available in Europe. One of the most common treatment-related side effects observed has been the mogamulizumab-associated rash (MAR), which affects up to a quarter of patients and is the most frequent adverse event leading to drug discontinuation. The aim of this study is to perform a systematic review of the literature on patients diagnosed with MAR and other mogamulizumab-related cutaneous events to describe the clinical and histological characteristics, the management in clinical practice and to assess whether these events have prognostic implications. In total, 2073 records were initially identified through a literature search, 843 of which were duplicates. After screening for eligibility and inclusion criteria, 49 articles reporting mogamulizumab-associated cutaneous events were included. Totally, 1516 patients were retrieved, with a slight male prevalence as for the available data (639 males and 570 females, i.e. 52.9% vs. 47.1%). Regarding the reported clinicopathological findings of the cutaneous reactions, the five most common patterns were spongiotic/psoriasiform dermatitis (22%), eruptions characterized by the presence of papules and/or plaques (16.1%), cutaneous granulomatosis (11.4%), morbilliform or erythrodermic dermatitis (9.4%) and photodermatitis (7.1%). Our results highlight how the majority of the reported cutaneous adverse events on mogamulizumab are of mild-to-moderate entity and generally manageable in clinical practice, though prompt recognition is essential and case-by-case assessment should be recommended. Future research will need to focus on the MAR prognostic implications and to identify genomic and molecular markers for a more rapid and accurate diagnosis.

Downstream STING pathways IRF3 and NF-κB differentially regulate CCL22 in response to cytosolic dsDNA

Double-stranded DNA (dsDNA) in the cytoplasm of eukaryotic cells is abnormal and typically indicates the presence of pathogens or mislocalized self-DNA. Multiple sensors detect cytosolic dsDNA and trigger robust immune responses via activation of type I interferons. Several cancer immunotherapy treatments also activate cytosolic nucleic acid sensing pathways, including oncolytic viruses, nucleic acid-based cancer vaccines, and pharmacological agonists. We report here that cytosolic dsDNA introduced into malignant cells can robustly upregulate expression of CCL22, a chemokine responsible for the recruitment of regulatory T cells (Tregs). Tregs in the tumor microenvironment are thought to repress anti-tumor immune responses and contribute to tumor immune evasion. Surprisingly, we found that CCL22 upregulation by dsDNA was mediated primarily by interferon regulatory factor 3 (IRF3), a key transcription factor that activates type I interferons. This finding was unexpected given previous reports that type I interferon alpha (IFN-α) inhibits CCL22 and that IRF3 is associated with strong anti-tumor immune responses, not Treg recruitment. We also found that CCL22 upregulation by dsDNA occurred concurrently with type I interferon beta (IFN-β) upregulation. IRF3 is one of two transcription factors downstream of the STimulator of INterferon Genes (STING), a hub adaptor protein through which multiple dsDNA sensors transmit their signals. The other transcription factor downstream of STING, NF-κB, has been reported to regulate CCL22 expression in other contexts, and NF-κB has also been associated with multiple pro-tumor functions, including Treg recruitment. However, we found that NF-κB in the context of activation by cytosolic dsDNA contributed minimally to CCL22 upregulation compared with IRF3. Lastly, we observed that two strains of the same cell line differed profoundly in their capacity to upregulate CCL22 and IFN-β in response to dsDNA, despite apparent STING activation in both cell lines. This finding suggests that during tumor evolution, cells can acquire, or lose, the ability to upregulate CCL22. This study adds to our understanding of factors that may modulate immune activation in response to cytosolic DNA and has implications for immunotherapy strategies that activate DNA sensing pathways in cancer cells.

Mogamulizumab Combined with Extracorporeal Photopheresis as a Novel Therapy in Erythrodermic Cutaneous T-cell Lymphoma

BACKGROUND

Primary cutaneous T-cell lymphomas (CTCLs) are rare lymphoproliferative malignancies characterized by significant morbidity and mortality in advanced disease stages. As curative approaches apart from allogeneic stem cell transplantation are lacking, establishing new treatment options, especially combination therapies, is crucial.

METHODS

This retrospective study included 11 patients with SS or MF receiving therapy with mogamulizumab in combination with ECP from four European expert centers. The response rates in the skin and blood as well as treatment use and adverse events (AE) were described.

RESULTS

8/11 patients (73%) showed an overall response (OR) in the skin. The mean mSWAT decreased from 98.2 ± 40.8 to 34.6 ± 23.8. The overall response rate (ORR) in the blood was 64% with two complete responses. During combination therapy, the mean number of Sézary cells decreased from 3365.3 × 106/L before treatment to 1268.6 × 106/L. The mean minimum known period without progress was 7.2 months in the skin and 7.6 months in the blood. The most common AEs were mogamulizumab-associated rash (MAR) (45.5%), anemia (27.3%), lymphocytopenia (27.8%), and infusion related reaction (16.7%). No AE led to treatment discontinuation.

CONCLUSIONS

Our study presents the combination of mogamulizumab and ECP as an effective therapy in the blood and skin in CTCL with good tolerability, similar to mogamulizumab monotherapy.

Effectiveness of mogamulizumab in patients with Mycosis Fungoides or Sézary syndrome: A multicentre, retrospective, real-world French study

BACKGROUND

Efficacy and safety of mogamulizumab, a monoclonal antibody directed against C-C chemokine receptor 4, were demonstrated in a previous multinational clinical trial conducted in patients with previously treated cutaneous T-cell lymphoma (CTCL): Sézary syndrome (SS) or Mycosis Fungoides (MF).

OBJECTIVES

The real-world French OMEGA study aimed to describe effectiveness and tolerability of mogamulizumab in adult patients with CTCL, overall and according to the disease (SS or MF).

METHODS

In this retrospective study, patients treated with mogamulizumab for SS or MF were included from 14 French expert centres. The overall response rate (ORR) under treatment was described (primary criterion), as well as treatment use and safety data.

RESULTS

The 122 analysed patients (69 SS, 53 MF) were aged 66.6 ± 12.1 years at mogamulizumab initiation, and their median disease duration was 2.5 years (IQR: 1.3-5.6). Prior to treatment start, they received a median of three systemic CTCL therapies (2-5). Overall, 77.8% of patients suffered from advanced disease (Stage IIB-IVB), with frequent blood (B1/B2) involvement (67.5%). Over the treatment period (median: 4.6 months, 2.1-7.2), 96.7% of patients received all the planned mogamulizumab infusions. Among the 109 patients evaluable for effectiveness, ORR was 58.7% (95% CI [48.9-68.1]) overall, 69.5% [56.1-80.8] in SS and 46.0% [31.8-60.7] in MF. Compartmental response in the blood was observed in 81.8% [69.1-90.9] of SS patients. Skin responses were observed in 57.0% [47.0-66.5] of patients overall, 66.7% [52.9-78.6] in SS and 46.0% [31.8-60.7] in MF. The most common serious adverse drug reactions were rash (8.1% of patients) and infusion-related reactions (2.4%) which led to treatment discontinuation in 7.3% and 0.8% of patients, respectively. One patient with SS died from mogamulizumab-related tumour lysis syndrome.

CONCLUSIONS

This large French study confirmed the effectiveness and tolerability of mogamulizumab in SS and MF patients in routine medical practice.

Tumor-infiltrating regulatory T cells as targets of cancer immunotherapy

Regulatory T cells (Tregs) are abundant in tumor tissues, raising a question of whether immunosuppressive tumor-infiltrating Tregs (TI-Tregs) can be selectively depleted or functionally attenuated to evoke effective anti-tumor immune responses by conventional T cells (Tconvs), without perturbing Treg-dependent immune homeostasis in healthy organs and causing autoimmunity. Here, we review current cancer immunotherapy strategies, including immune checkpoint blockade (ICB) antibodies against CTLA-4 and PD-1 and discuss their effects on TI-Tregs. We also discuss approaches that exploit differentially regulated molecules on the cell surface (e.g., CTLA-4) and intracellularly (e.g., T cell receptor signaling molecules) between TI-Tregs and Tconvs as well as their dependence on cytokines (e.g., IL-2) and metabolites (e.g., lactate). We envisage that targeting TI-Tregs could be effective as a monotherapy and/or when combined with ICB antibodies.

[18F]FDG PET/CT in a Case of Mycosis Fungoides Showing an Unusual Adverse Reaction to Mogamulizumab: Correlation Between Imaging and Histological Findings

A 73-year-old female patient, affected by mycosis fungoides (MF), discontinued mogamulizumab, after initial clinical benefit, due to the onset of generalized erythema. Follow-up positron emission computed tomography (PET/CTs) carried out at 3 weeks and 6 months after therapy discontinuation showed, with respect to baseline PET/CT scan, a progressively increasing number of hypermetabolic enlarged lymph nodes suspected for a neoplastic involvement, but with histology indicative of an inflammatory reaction. After sequential therapy with corticosteroids and methotrexate, a complete remission was registered at 18F-fluorodeoxyglucose ([¹⁸F]FDG) PET/CT performed at 12 months after mogamulizumab interruption. The case we describe highlights the usefulness of serial examinations with [¹⁸F]FDG PET/CT in an MF patient presenting an unusual adverse reaction to mogamulizumab.

Physiology of chemokines in the cancer microenvironment

Chemokines are chemotactic cytokines whose canonical functions govern movement of receptor-expressing cells along chemical gradients. Chemokines are a physiological system that is finely tuned by ligand and receptor expression, ligand or receptor oligomerization, redundancy, expression of atypical receptors, and non-GPCR binding partners that cumulatively influence discrete pharmacological signaling responses and cellular functions. In cancer, chemokines play paradoxical roles in both the directed emigration of metastatic, receptor-expressing cancer cells out of the tumor as well as immigration of tumor-infiltrating immune cells that culminate in a tumor-unique immune microenvironment. In the age of precision oncology, strategies to effectively harness the power of immunotherapy requires consideration of chemokine gradients within the unique spatial topography and temporal influences with heterogeneous tumors. In this article, we review current literature on the diversity of chemokine ligands and their cellular receptors that detect and process chemotactic gradients and illustrate how differences between ligand recognition and receptor activation influence the signaling machinery that drives cellular movement into and out of the tumor microenvironment. Facets of chemokine physiology across discrete cancer immune phenotypes are contrasted to existing chemokine-centered therapies in cancer.

Quality of Life in Cutaneous T-cell Lymphoma Patients Receiving Mogamulizumab: Important Factors to Consider

BACKGROUND

Erythrodermic cutaneous T-cell lymphoma (E-CTCL) is associated with a poor prognosis and severe symptoms.

OBJECTIVE

To establish insights into the quality of life (QoL), expectations, and treatment satisfaction of E-CTCL patients receiving mogamulizumab.

METHODS

Outcomes of this prospective cohort study conducted between September 2020 and August 2021 at the Leiden University Medical Center included the dermatology-specific QoL (Skindex-29), health-related QoL (RAND-12), degree of itch, pain, and fatigue (Visual Analogue Scale), patient's expectations, and treatment satisfaction (Client Satisfaction Questionnaire-8 (CSQ-8)), measured at baseline and after six months.

RESULTS

13 patients with E-CTCL were included. Most patients anticipated a positive treatment effect on symptoms. Five patients (46%) improved one or more clinical categories regarding the symptoms domain, six (55%) regarding emotions, four (36%) regarding functioning, and four (36%) regarding the overall Skindex-29 score compared to baseline. The Mental Component Score clinically improved from 31 (IQR 29-51) at baseline to 38 (IQR 25-51). The median VAS itch improved significantly from baseline (8 (IQR 7-10) vs. 3 (IQR 1-8), p = 0.024). Most patients (n = 7) were "very satisfied" with their treatment.

LIMITATIONS

There was a limited number of patients due to the rarity of the disease.

CONCLUSION

In general, mogamulizumab has a favorable effect on biochemical- and dermatology-specific QoL and physical functioning in some patients, with high treatment satisfaction. Itch especially improved over time in most patients. The treatment satisfaction was generally high. Mogamulizumab seems to be an effective treatment that improves the QoL in patients with E-CTCL.

Trametinib improves Treg selectivity of anti-CCR4 antibody by regulating CCR4 expression in CTLs in oral squamous cell carcinoma

Regulatory T-cells (Tregs) play a major role in suppressing anti-tumor immune responses. Mogamulizumab, an anti-CC chemokine receptor type 4 (CCR4) monoclonal antibody, depletes effector Tregs (eTregs). However, the clinical efficacy of mogamulizumab was limited in phase Ia/Ib studies for solid tumors (NCT01929486); the finding suggests that mogamulizumab may also deplete beneficial CCR4⁺CD8⁺ T-cells in patients. Therefore, we focused on CTLs and aimed to identify a way to protect CCR4⁺ CTLs. Here, we evaluated the association of CCR4 expression in cytotoxic T-lymphocytes (CTLs) with antigen and cytokine stimulations and kinase inhibition using cytomegalovirus antigen instead of tumor antigen. CCR4 expression in CTLs was induced by antigen stimulation (mean 3.14-29.0%), enhanced by transforming growth factor-β1 (TGF-β1) (mean 29.0-51.2%), and downregulated by trametinib with (mean 51.2-11.4%) or without TGF-β1 treatment (mean 29.0-6.98%). Phosphorylation of ERK in CD8⁺ T-cells was suppressed by trametinib. Regarding the effect on immunological function of CTL, trametinib reduced cytokine production but not affected cytotoxicity. Importantly, trametinib alleviated CTL reduction by anti-CCR4 antibody without affecting eTreg depletion because CCR4 expression in eTregs was not downregulated. In conclusion, combination therapy with trametinib may improve the clinical efficacy of mogamulizumab.

Surgery-mediated tumor-promoting effects on the immune microenvironment

Surgical resection continues to be the mainstay treatment for solid cancers even though chemotherapy and immunotherapy have significantly improved patient overall survival and progression-free survival. Numerous studies have shown that surgery induces the dissemination of circulating tumor cells (CTCs) and that the resultant inflammatory response promotes occult tumor growth and the metastatic process by forming a supportive tumor microenvironment (TME). Surgery-induced platelet activation is one of the initial responses to a wound and the formation of fibrin clots can provide the scaffold for recruited inflammatory cells. Activated platelets can also shield CTCs to protect them from blood shear forces and promote CTCs evasion of immune destruction. Similarly, neutrophils are recruited to the fibrin clot and enhance cancer metastatic dissemination and progression by forming neutrophil extracellular traps (NETs). Activated macrophages are also recruited to surgical sites to facilitate the metastatic spread. More importantly, the body's response to surgical insult results in the recruitment and expansion of immunosuppressive cell populations (i.e. myeloid-derived suppressor cells and regulatory T cells) and in the suppression of natural killer (NK) cells that contribute to postoperative cancer recurrence and metastasis. In this review, we seek to provide an overview of the pro-tumorigenic mechanisms resulting from surgery's impact on these cells in the TME. Further understanding of these events will allow for the development of perioperative therapeutic strategies to prevent surgery-associated metastasis.

A review on targeting tumor microenvironment: The main paradigm shift in the mAb-based immunotherapy of solid tumors

Monoclonal antibodies (mAbs) as biological macromolecules have been remarked the large and growing pipline of the pharmaceutical market and also the most promising tool in modern medicine for cancer therapy. These therapeutic entities, which consist of whole mAbs, armed mAbs (i.e., antibody-toxin conjugates, antibody-drug conjugates, and antibody-radionuclide conjugates), and antibody fragments, mostly target tumor cells. However, due to intrinsic heterogeneity of cancer diseases, tumor cells targeting mAb have been encountered with difficulties in their unpredictable efficacy as well as variability in remission and durable clinical benefits among cancer patients. To address these pitfalls, the area has undergone two major evolutions with the intent of minimizing anti-drug responses and addressing limitations experienced with tumor cell-targeted therapies. As a novel hallmark of cancer, the tumor microenvironment (TME) is becoming the great importance of attention to develop innovative strategies based on therapeutic mAbs. Here, we underscore innovative strategies targeting TME by mAbs which destroy tumor cells indirectly through targeting vasculature system (e.g., anti-angiogenesis), immune system modulation (i.e., stimulation, suppression, and depletion), the targeting and blocking of stroma-based growth signals (e.g., cancer-associated fibroblasts), and targeting cancer stem cells, as well as, their effector mechanisms, clinical uses, and relevant mechanisms of resistance.

Impact of Mogamulizumab in Real-Life Advanced Cutaneous T-Cell Lymphomas: A Multicentric Retrospective Cohort Study

Simple Summary

Mogamulizumab is a recent monoclonal antibody prescribed in the second line to treat advanced mycosis fungoides and Sézary syndromes. We collected data from all patients who used mogamulizumab in six French university hospitals until 1 September 2021. Our primary objective was to determine the median progression free survival (PFS). Secondary objectives were to consider tolerance regarding side effect occurrence and severity. Twenty-one patients were included, with a median time of follow-up of 11.6 months, and progression-free survival was estimated at 22 months. Twenty patients presented adverse events, of which 10 were severe. The median time between the introduction of mogamulizumab and the first adverse event was 21 days. Our study suggests that mogamulizumab is a significant treatment option to extend PFS in patients with advanced refractory cutaneous T-cell lymphomas (CTCL). The long-term safety of mogamulizumab was determined to be acceptable since we reported few grade III–IV adverse events (AEs) compared to other systemic treatments.

Abstract

Background: Advanced mycosis fungoides (MF) and Sézary syndrome (SS) are rare, aggressive cutaneous T-cell lymphomas that may be difficult to treat. Mogamulizumab is a recent monoclonal antibody targeting the CCR4 receptor expressed on the surface of Sézary cells. It can be prescribed in MF/SS stages III to IV in the second line after systemic therapy or in stages IB-II after two unsuccessful systemic therapies. We lack data on long-term efficiency and potential side effects in real-life conditions. Our study aims to determine efficacy considering the median PFS of advanced CTCL with mogamulizumab. Secondary objectives were to consider tolerance and estimate delay until side effects appeared. Methods: Data on patients with advanced cutaneous T-cell lymphomas were collected since French Authorization, in six French university hospitals. Patients were followed until they stopped mogamulizumab because of relapse or toxicity. For those still treated by mogamulizumab, the end point was 1 September 2021. We excluded 3 patients as they had already been included in the MAVORIC study and data was not available. Results: The median time of follow-up was 11.6 months. Of the 21 patients included, we reported four full-response patients, eight in partial response, one in stability, three in progression, and five were deceased. One patient had visceral progression, and seven had new lymphadenopathy. Progression-free survival was estimated at 22 months. Twenty patients presented adverse events, of which 10 were severe, i.e., grade III-IV. The median time between the introduction of mogamulizumab and the first adverse event was 21 days. Conclusions: Our study suggests that mogamulizumab can give patients with advanced refractory CTCL a consequent PFS, estimated at 22 months. The long-term safety of mogamulizumab was determined to be acceptable since we reported few grade III–IV AEs, comparable with other studies. No other study using real-life data has been performed to investigate the AEs of mogamulizumab.

CCR4 as a Therapeutic Target for Cancer Immunotherapy

Simple Summary

CCR4 is a chemokine receptor selectively expressed on normal T cell subsets such as type 2 helper T cells, skin-homing T cells and regulatory T cells, and on skin-associated T cell malignancies such as adult T cell leukemia/lymphoma (ATLL), which is etiologically associated with human T lymphocyte virus type 1 (HTLV-1), and cutaneous T cell lymphomas (CTCLs). Mogamulizumab is a fully humanized and glyco-engineered monoclonal anti-CCR4 antibody used for the treatment of refractory/relapsed ATLL and CTCLs, often resulting in complete remission. The clinical applications of Mogamulizumab are now being extended to solid tumors, exploring the therapeutic effect of regulatory T cell depletion. This review overviews the expression of CCR4 in various T cell subsets, HTLV-1-infected T cells, ATLL and CTCLs, and the clinical applications of Mogamulizumab.

Abstract

CCR4 is a chemokine receptor mainly expressed by T cells. It is the receptor for two CC chemokine ligands, CCL17 and CCL22. Originally, the expression of CCR4 was described as highly selective for helper T type 2 (Th2) cells. Later, its expression was extended to other T cell subsets such as regulatory T (Treg) cells and Th17 cells. CCR4 has long been regarded as a potential therapeutic target for allergic diseases such as atopic dermatitis and bronchial asthma. Furthermore, the findings showing that CCR4 is strongly expressed by T cell malignancies such as adult T cell leukemia/lymphoma (ATLL) and cutaneous T cell lymphomas (CTCLs) have led to the development and clinical application of the fully humanized and glyco-engineered monoclonal anti-CCR4 Mogamulizumab in refractory/relapsed ATLL and CTCLs with remarkable successes. However, Mogamulizumab often induces severe adverse events in the skin possibly because of its efficient depletion of Treg cells. In particular, treatment with Mogamulizumab prior to allogenic hematopoietic stem cell transplantation (allo-HSCT), the only curative option of these T cell malignancies, often leads to severe glucocorticoid-refractory graft-versus-host diseases. The efficient depletion of Treg cells by Mogamulizumab has also led to its clinical trials in advanced solid tumors singly or in combination with immune checkpoint inhibitors. The main focus of this review is CCR4; its expression on normal and malignant T cells and its significance as a therapeutic target in cancer immunotherapy.