Infusion-Related Reactions Subsequent to Avelumab, Durvalumab, and Atezolizumab Administration: A Retrospective Observational Study.

BACKGROUND: Avelumab, durvalumab, and atezolizumab are anti-programmed death-ligand 1 (PD-L1) antibodies approved for clinical application in Japan. Despite targeting the same molecule, avelumab elicits a different frequency of infusion-related reactions (IRRs) compared with durvalumab and atezolizumab, leading to differences in premedication recommendations. This study aimed to collect information to verify the relationship during IRRs and the characteristics of antibody molecules, by investigating the frequency of IRRs caused by three types of antibodies and the actual status of prophylactic measures. METHODS: This single-center, retrospective observational study collected the medical records of 73 patients who received avelumab, durvalumab, or atezolizumab at Osaka University Hospital. RESULTS: The frequency of IRRs was 50.0% (12/24) for avelumab, 31.0% (8/27) for durvalumab, and 18.2% (4/22) for atezolizumab. The IRRs were grade 2 in seven patients and grade 1 in five patients treated with avelumab, grade 2 in six patients and grade 1 in two patients treated with durvalumab, and grade 1 in all patients treated with atezolizumab. Among patients in whom symptoms were observed during the first administration, measures were taken to prevent IRRs for the second administration, but cases were confirmed in which symptoms reappeared, especially in patients who received durvalumab. CONCLUSION: Our findings indicate that the frequency of IRRs due to anti-PD-L1 antibodies is higher than that previously reported in clinical trials and different modifications in antibody molecules may affect the difference in IRR frequency.

Binding and Efficacy of Anti-Robo4 CAR-T Cells against Solid Tumors.

Chimeric antigen receptor expression T (CAR-T) cell therapy has been shown be efficacious against relapsed/refractory B-cell malignant lymphoma and has attracted attention as an innovative cancer treatment. However, cells of solid tumors are less accessible to CAR-T cells; moreover, CAR-T function is decreased in the immunosuppressive state of the tumor microenvironment. Since most tumors induce angiogenesis, we constructed CAR-T cells targeting roundabout homolog 4 (Robo4), which is expressed at high levels in tumor vascular endothelial cells, by incorporating three anti-Robo4 single-chain variable fragments (scFv) that were identified using phage display. We found that binding affinities of the three CARs to mouse and human Robo4 reflected their scFv affinities. More importantly, when each CAR-T cell was assayed in vitro, antigen-specific cytotoxicity, cytokine-producing ability, and proliferation were correlated with binding affinity for Robo4. In vivo, all three T-cells inhibited tumor growth in a B16BL6 murine model, which also correlated with Robo4 binding affinities. However, growth inhibition of mouse Robo4-expressing tumors was observed only in the model with CAR-T cells with the lowest Robo4 affinity. Therefore, at high Robo4 expression, CAR-T in vitro and in vivo were no longer correlated, suggesting that clinical tumors will require Robo4 expression assays.

The Effects of Chimeric Antigen Receptor (CAR) Hinge Domain Post-Translational Modifications on CAR-T Cell Activity.

To improve the efficacy and safety of chimeric antigen receptor (CAR)-expressing T cell therapeutics through enhanced CAR design, we analysed CAR structural factors that affect CAR-T cell function. We studied the effects of disulphide bonding at cysteine residues and glycosylation in the HD on CAR-T function. We used first-generation CAR[V/28/28/3z] and CAR[V/8a/8a/3z], consisting of a mouse vascular endothelial growth factor receptor 2 (VEGFR2)-specific single-chain variable fragment tandemly linked to CD28- or CD8α-derived HD, transmembrane domain (TMD) and a CD3ζ-derived signal transduction domain (STD). We constructed structural variants by substituting cysteine with alanine and asparagine (putative N-linked glycosylation sites) with aspartate. CAR[V/28/28/3z] and CAR[V/8a/8a/3z] formed homodimers, the former through a single HD cysteine residue and the latter through the more TMD-proximal of the two cysteine residues. The absence of disulphide bonds did not affect membrane CAR expression but reduced antigen-specific cytokine production and cytotoxic activity. CAR[V/28/28/3z] and CAR[V/8a/8a/3z] harboured one N-linked glycosylation site, and CAR[V/8a/8a/3z] underwent considerable O-linked glycosylation at an unknown site. Thus, N-linked glycosylation of CAR[V/28/28/3z] promotes stable membrane CAR expression, while having no effect on the expression or CAR-T cell activity of CAR[V/8a/8a/3z]. Our findings demonstrate that post-translational modifications of the CAR HD influence CAR-T cell activity, establishing a basis for future CAR design.

Transcutaneous Administration of Imiquimod Promotes T and B Cell Differentiation into Effector Cells or Plasma Cells.

We are interested in promoting the development of transcutaneous immunization using microneedle technology and attempting to apply an adjuvant with transcutaneous immunization to improve the efficacy and reduce the amount of antigen and number of administrations needed. In this study, we collected basic information to help elucidate the mechanism responsible for the transcutaneous adjuvant activity of imiquimod (IMQ), which is a ligand of toll-like receptor (TLR) 7. In mouse groups administered ovalbumin (OVA), the OVA-specific IgG antibody titer of the IMQ-adjuvanted group was higher than that of the group administered OVA alone. No immune response bias due to transcutaneous IMQ administration was observed in terms of IgG1 (T helper cell [Th]2-type IgG subclass) and IgG2c (Th1-type IgG subclass) antibody titers. After the initial immunization, the IMQ-adjuvanted group showed increased migration of Langerhans cells to draining lymph nodes (dLNs) and active proliferation of OVA-specific CD4+ T cells. Transcutaneously administered IMQ did not affect the direction of CD4+ T cell differentiation, while promoted B cell activation and germinal center (GC) B cell differentiation. Immune staining revealed greater GC formation in the dLNs with the IMQ-adjuvanted group than in the OVA-alone group. In the secondary immune response, effector T cells increased in the dLNs and spleen, and effector memory T cells also increased in the spleen in the IMQ-adjuvanted group. In addition, our results suggested that the administration of IMQ enhanced B cell differentiation into plasma cells and GC B cells in the dLNs and spleen. In this study, we partially clarified the mechanism underlying the adjuvant activity of transcutaneously administered IMQ, which is required for the practical application of transcutaneous immunization with IMQ.

Analysis of immune response induction mechanisms implicating the dose-sparing effect of transcutaneous immunization using a self-dissolving microneedle patch.

Transcutaneous immunization (TCI) is an effective vaccination method that is easier and less painful than the conventional injectable vaccination method. We previously developed self-dissolving microneedle patches (sdMN) and demonstrated that this TCI method has a high vaccination efficacy in mice and humans. To elucidate the mechanism of immune response induction, which is the basis for the efficacy and safety of TCI with sdMN, we examined the local reaction of the skin where sdMN was applied and the kinetics and differentiation status of immune cells in the draining lymph nodes (DLNs). We found that gene expression of the proinflammatory cytokine Il1b and the downstream transcription factor Irf7 was markedly upregulated in skin tissues after sdMN application. Moreover, activation of Langerhans cells and CD207- dermal dendritic cells, which are subsets of antigen-presenting cells (APCs) in the skin, and their migration to the DLNs were promoted. Furthermore, the activated APC subsets promoted CD4+ T cell and B cell differentiation and the formation of germinal centers, which are the sites of high-affinity antibody production. These phenomena associated with sdMN application may contribute to the efficient production of antigen-specific antibodies after TCI using sdMN. These findings provide essential information regarding immune response induction mechanisms for the development and improvement of TCI preparations.

Vascular Endothelial Growth Factor Receptor Inhibitors Impair Left Ventricular Diastolic Functions.

Vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) frequently induce cardiovascular adverse events, though VEGFR-TKIs contribute to the improvement of the prognosis of patients with malignancies. It is widely accepted that VEGFR-TKIs impair left ventricular systolic functions; however, their effects on diastolic functions remain to be fully elucidated. The purpose of this study was to analyze the impact of VEGFR-TKIs on left ventricular diastolic functions. This study was designed as a retrospective single-center cohort study in Japan. We assessed 24 cases who received VEGFR-TKI monotherapy (sunitinib, sorafenib, pazopanib, axitinib) with left ventricular ejection fraction (LVEF) above 50% during the therapy at the Osaka University Hospital from January 2008 to June 2019. Left ventricular diastolic functions were evaluated by the change in echocardiographic parameters before and after the VEGFR-TKI treatment. Both septal e' and lateral e's decreased after treatment (septal e': before, 6.1 ± 1.8; after, 5.0 ± 1.9; n = 21, P < 0.01; lateral e': before, 8.7 ± 2.8; after, 6.9 ± 2.3; n = 21, P < 0.01). E/A declined after VEGFR-TKIs administration, though not statistically significantly. In 20 cases with at least one risk factor for heart failure with preserved ejection fraction (HFpEF), E/A significantly decreased (0.87 ± 0.34 versus 0.68 ± 0.14; P < 0.05) as well as the septal and lateral e's. These results suggest that treatment with VEGFR-TKIs impairs left ventricular diastolic functions in patients with preserved LVEF, especially in those with risk factors for HFpEF.

Adjuvant Activity of CpG-Oligonucleotide Administered Transcutaneously in Combination with Vaccination Using a Self-Dissolving Microneedle Patch in Mice.

In this study, we investigated the mechanism of transcutaneous adjuvant activity of the CpG-oligonucleotide (K3) in mice. Transcutaneous immunization (TCI) with an ovalbumin-loaded self-dissolving microneedle patch (OVA-sdMN) and K3-loaded hydrophilic gel patch (HG) increased OVA-specific Th2- and Th1-type IgG subclass antibody titers more rapidly and strongly than those after only OVA-sdMN administration. However, the antigen-specific proliferation of OVA-specific CD4+ T cells was similar between the OVA-only and the OVA+K3 groups. Population analysis of various immune cells in draining lymph nodes (dLNs) in the primary immune response revealed that the OVA+K3 combination doubled the number of dLN cells, with the most significant increase in B cells. Phenotypic analysis by flow cytometry revealed that B-cell activation and maturation were promoted in the OVA+K3 group, suggesting that direct B-cell activation by K3 largely contributed to the rapid increase in antigen-specific antibody titer in TCI. In the secondary immune response, a significant increase in effector T cells and effector memory T cells, and an increase in memory B cells were observed in the OVA+K3 group compared with that in the OVA-only group. Thus, K3, as a transcutaneous adjuvant, can promote the memory differentiation of T and B cells.

Characteristics of immune induction by transcutaneous vaccination using dissolving microneedle patches in mice.

Transcutaneous immunization (TCI) is an appealing vaccination method. Compared with conventional injectable immunization, TCI is easier and less painful. We previously developed a dissolving microneedle (MN) patch and demonstrated that TCI using MN patches demonstrates high vaccination efficacy without adverse events in humans. In this study, we investigated the immune induction mechanism of TCI using our MN patch, focusing on inflammatory responses in the skin and on the dynamics, activation, and differentiation of various immunocompetent cells in draining lymph nodes (dLNs). We demonstrate that inflammatory cytokines such as IL-6 and TNF-α increased in the skin at an early stage after MN patch application, inducing the infiltration of macrophages and neutrophils and promoting the activation and migration of skin-resident antigen-presenting cells (Langerhans and Langerin- dermal dendritic cells) to dLNs. Moreover, the activated antigen-presenting cells reaching the dLNs enhanced the differentiation of T (Teff, Tem, and Tcm) and B (plasma and memory) cells. This may contribute to the efficient antigen-specific antibody production induced by TCI using MN patches. We believe that our findings reveal a part of the immune induction mechanism by TCI and provide useful information for the development and improvement of TCI formulations based on the immune induction mechanism.

Characteristic of K3 (CpG-ODN) as a Transcutaneous Vaccine Formulation Adjuvant.

Transcutaneous immunization (TCI) is easy to use, minimally invasive, and has excellent efficacy in vaccines against infections. We focused on toll-like receptor (TLR) ligands as applicable adjuvants for transcutaneous formulations and characterized immune responses. TCI was performed using poke-and-patch methods, in which puncture holes are formed with a polyglycolic acid microneedle on the back skin of mice. Various TLR ligands were applied to the puncture holes and covered with an ovalbumin-loaded hydrophilic gel patch. During the screening process, K3 (CpG-oligonucleotide) successfully produced more antigen-specific antibodies than other TLR ligands and induced T helper (Th) 1-type polarization. Transcutaneously administered K3 was detected in draining lymph nodes and was found to promote B cell activation and differentiation, suggesting a direct transcutaneous adjuvant activity on B cells. Furthermore, a human safety test of K3-loaded self-dissolving microneedles (sdMN) was performed. Although a local skin reaction was observed at the sdMN application site, there was no systemic side reaction. In summary, we report a K3-induced Th1-type immune response that is a promising adjuvant for transcutaneous vaccine formulations using MN and show that K3-loaded sdMN can be safely applied to human skin.

Immunogenicity of Milk Protein-Containing Hydrophilic Gel Patch for Epicutaneous Immunotherapy for Milk Allergy.

PURPOSE: Epicutaneous immunotherapy (EPIT) involving the skin's immune system is easy to use, painless and has a low risk of systemic side effects; it can be applied to food allergies that have a high morbidity rate in children. In this study, we evaluated the safety and efficacy of hydrophilic gel patch (HG) for EPIT. METHODS: Milk protein concentrate (MPC)-containing HG was applied to the skin that maintained a barrier function or formed puncture holes with microneedle, and MPC-specific antibodies were measured. The clinical study was conducted involving patients with severe milk allergy. RESULTS: No specific immune response was induced when immunizing to intact skin, and antibody production was observed by forming puncture holes. It was suggested that MPC contained in HG has immunogenicity and a very small amount of MPC was delivered to intact skin. In the clinical study, the symptom induction threshold increased in four of eight subjects, allowing them to consume milk and switch to oral immunotherapy. Although local skin reactions and temporary elevation of specific IgE antibodies were observed, no systemic side effects appeared throughout the study. CONCLUSIONS: EPIT using HG is a safe method to enable oral administration even in patients with severe milk allergies.

Verification of pharmacogenomics-based algorithms to predict warfarin maintenance dose using registered data of Japanese patients.

PURPOSE: Large inter-individual differences in warfarin maintenance dose are mostly due to the effect of genetic polymorphisms in multiple genes, including vitamin K epoxide reductase complex 1 (VKORC1), cytochromes P450 2C9 (CYP2C9), and cytochrome P450 4F2 (CYP4F2). Thus, several algorithms for predicting the warfarin dose based on pharmacogenomics data with clinical characteristics have been proposed. Although these algorithms consider these genetic polymorphisms, the formulas have different coefficient values that are critical in this context. In this study, we assessed the mutual validity among these algorithms by specifically considering racial differences. METHODS: Clinical data including actual warfarin dose (AWD) of 125 Japanese patients from our previous study (Eur J Clin Pharmacol 65(11):1097-1103, 2009) were used as registered data that provided patient characteristics, including age, sex, height, weight, and concomitant medications, as well as the genotypes of CYP2C9 and VKORC1. Genotyping for CYP4F2*3 was performed by the PCR method. Five algorithms that included these factors were selected from peer-reviewed articles. The selection covered four populations, Japanese, Chinese, Caucasian, and African-American, and the International Warfarin Pharmacogenetics Consortium (IWPC). RESULTS: For each algorithm, we calculated individual warfarin doses for 125 subjects and statistically evaluated its performance. The algorithm from the IWPC had the statistically highest correlation with the AWD. Importantly, the calculated warfarin dose (CWD) using the algorithm from African-Americans was less correlated with the AWD as compared to those using the other algorithms. The integration of CYP4F2 data into the algorithm did not improve the prediction accuracy. CONCLUSION: The racial difference is a critical factor for warfarin dose predictions based on pharmacogenomics.

Correction: Development of Novel Faster-Dissolving Microneedle Patches for Transcutaneous Vaccine Delivery. Pharmaceutics, 2017, 9(3), 27.

The authors wish to make a change to their published paper [1].[...].

Development of novel double-decker microneedle patches for transcutaneous vaccine delivery.

Microneedle (MN) patches have great potential as transcutaneous vaccine delivery devices because MNs can effectively deliver vaccine antigen into the skin through the micropores formed in the stratum corneum by low-invasive and painless skin puncturing. This study aims to develop novel double-decker MN patches which have not only high safety and efficacy but also broad applicability to various vaccine antigens. We developed two types of MN patches (PGA-MN and Nylon-MN) that are made from polyglycolic acid and Nylon-6. In pre-clinical studies, both MN patches could demonstrably deliver antigens into resected human dermal tissue, prolong antigen deposition and increase antigen-specific IgG levels after vaccination compared with conventional injections. We demonstrated both MN patches could be safely applied to human skin because no broken MNs or significant skin irritation were observed after applications in the clinical research. PGA-MN was suggested to be superior to Nylon-MN regarding human skin puncturability based on measurements of transepidermal water loss and needle failure force. A high content of tetravalent influenza hemagglutinin antigens loaded on PGA-MN could stably maintain HA titers at 35°C for 1year. Overall, double-decker MN patches can reliably and safely puncture human skin and are promising as effective transcutaneous vaccine delivery devices.

Development of Novel Faster-Dissolving Microneedle Patches for Transcutaneous Vaccine Delivery.

Microneedle (MN) patches are promising for transcutaneous vaccination because they enable vaccine antigens to physically penetrate the stratum corneum via low-invasive skin puncturing, and to be effectively delivered to antigen-presenting cells in the skin. In second-generation MN patches, the dissolving MNs release the loaded vaccine antigen into the skin. To shorten skin application time for clinical practice, this study aims to develop novel faster-dissolving MNs. We designed two types of MNs made from a single thickening agent, carboxymethylcellulose (CMC) or hyaluronan (HN). Both CMC-MN and HN-MN completely dissolved in rat skin after a 5-min application. In pre-clinical studies, both MNs could demonstrably increase antigen-specific IgG levels after vaccination and prolong antigen deposition compared with conventional injections, and deliver antigens into resected human dermal tissue. In clinical research, we demonstrated that both MNs could reliably and safely puncture human skin without any significant skin irritation from transepidermal water loss measurements and ICDRG (International Contact Dermatitis Research Group) evaluation results.

Clinical study of a retinoic acid-loaded microneedle patch for seborrheic keratosis or senile lentigo.

AIMS: Pigmented lesions such as of seborrheic keratosis and senile lentigo, which are commonly seen on skin of people>50years of age, are considered unattractive and disfiguring because of their negative psychological impact. Drug therapy using all-trans retinoic acid (ATRA) is an attractive option for self-treatment at home. We have developed an ATRA-loaded microneedle patch (ATRA-MN) and confirmed the pharmacological effects of ATRA-MN application in mice. Here, we describe a clinical study to evaluate the safety and efficacy of ATRA-MN in subjects with seborrheic keratosis or senile lentigo. MAIN METHODS: ATRA-MN was applied to the lesion site of each subject for 6h once per week for 4weeks. The skin irritation reaction was scored to assess adverse reactions and blood tests were performed to evaluate the presence of systemic adverse reactions. To assess the treatment effect using ATRA-MN, the desquamation and whitening ability of the investigational skin was observed. KEY FINDINGS: Desquamation of the stratum corneum was observed following four ATRA-MN applications at 1-week intervals, but ATRA-MN applications did not induce severe local or systemic adverse effects. SIGNIFICANCE: These results showed that ATRA-MN treatment is promising as a safe and effective therapy for seborrheic keratosis and senile lentigo.

Analysis of Skin Permeability and Toxicological Properties of Amorphous Silica Particles.

Nanomaterials (NMs) are defined as those which have nanostructured components less than 100 nm in diameter. They are widely used in various fields such as medicine, cosmetics, and the food industry. However, the toxicological effects of NMs are less well understood than their applications. In particular, the skin is exposed to the environment at all times, so is easily influenced by NMs. In this study, we investigated the skin permeability and toxicological properties of well-dispersed amorphous silica particles with diameters ranging from 70 to 1000 nm, to aid in the safe application of NMs. Amorphous silica particles of 70 nm in size (nSP70) penetrated the living epidermis, following pretreatment with acetone/diethyl ether to improve skin permeation. The application of unmodified nSP70, carboxyl group-modified nSP70, or amino group-modified nSP70 for long durations caused little skin irritation at the application site. Under the present experimental conditions, few adverse systemic effects were evident from blood tests and histopathologic examination. These results suggest that decreasing particle size increases the NMs skin permeability, but remarkably little corresponding skin irritation is observed.

Highly efficient gene transfer using a retroviral vector into murine T cells for preclinical chimeric antigen receptor-expressing T cell therapy.

Adoptive immunotherapy using chimeric antigen receptor-expressing T (CAR-T) cells has attracted attention as an efficacious strategy for cancer treatment. To prove the efficacy and safety of CAR-T cell therapy, the elucidation of immunological mechanisms underlying it in mice is required. Although a retroviral vector (Rv) is mainly used for the introduction of CAR to murine T cells, gene transduction efficiency is generally less than 50%. The low transduction efficiency causes poor precision in the functional analysis of CAR-T cells. We attempted to improve the Rv gene transduction protocol to more efficiently generate functional CAR-T cells by optimizing the period of pre-cultivation and antibody stimulation. In the improved protocol, gene transduction efficiency to murine T cells was more than 90%. In addition, almost all of the prepared murine T cells expressed CAR after puromycin selection. These CAR-T cells had antigen-specific cytotoxic activity and secreted multiple cytokines by antigen stimulation. We believe that our optimized gene transduction protocol for murine T cells contributes to the advancement of T cell biology and development of immunotherapy using genetically engineered T cells.

Clinical study and stability assessment of a novel transcutaneous influenza vaccination using a dissolving microneedle patch.

Transcutaneous immunization (TCI) is an attractive vaccination method compared with conventional injectable vaccines because it is easier to administer without pain. We developed a dissolving microneedle patch (MicroHyala, MH) made of hyaluronic acid and showed that transcutaneous vaccination using MH induced a strong immune response against various antigens in mice. In the present study, we investigated the clinical safety and efficacy of a novel transcutaneous influenza vaccine using MH (flu-MH), which contains trivalent influenza hemagglutinins (15 µg each). Subjects of the TCI group were treated transcutaneously with flu-MH, and were compared with subjects who received subcutaneous injections of a solution containing 15 µg of each influenza antigen (SCI group). No severe local or systemic adverse events were detected in either group and immune responses against A/H1N1 and A/H3N2 strains were induced equally in the TCI and SCI groups. Moreover, the efficacy of the vaccine against the B strain in the TCI group was stronger than that in the SCI group. Influenza vaccination using MH is promising for practical use as an easy and effective method to replace conventional injections systems.

Vaccine efficacy of transcutaneous immunization with amyloid ß using a dissolving microneedle array in a mouse model of Alzheimer's disease.

Vaccine therapy for Alzheimer's disease (AD) based on the amyloid cascade hypothesis has recently attracted attention for treating AD. Injectable immunization using amyloid ß peptide (Aß) comprising 1-42 amino-acid residues (Aß1-42) as antigens showed therapeutic efficacy in mice; however, the clinical trial of this injected Aß1-42 vaccine was stopped due to the incidence of meningoencephalitis caused by excess activation of Th1 cells infiltrating the brain as a serious adverse reaction. Because recent studies have suggested that transcutaneous immunization (TCI) is likely to elicit Th2-dominant immune responses, TCI is expected to be effective in treating AD without inducing adverse reactions. Previously reported TCI procedures employed complicated and impractical vaccination procedures; therefore, a simple, easy-to-use, and novel TCI approach needs to be established. In this study, we investigated the vaccine efficacy of an Aß1-42-containing TCI using our novel dissolving microneedle array (MicroHyala; MH) against AD. MH-based TCI induced anti-Aß1-42 immune responses by simple and low-invasive application of Aß1-42-containing MH to the skin. Unfortunately, this TCI system resulted in little significant improvement in cognitive function and Th2-dominant immune responses, suggesting the need for further modification.

Development of a novel therapeutic approach using a retinoic acid-loaded microneedle patch for seborrheic keratosis treatment and safety study in humans.

Seborrheic keratosis is one of the most common skin benign tumors in humans with a high occurrence rate of 80%-100% in people > 50 years of age; however, its pathogenesis is still unclear. The standard treatment includes cryotherapy and laser surgery for physically removing lesions. Drug therapy for this condition has not been well established. We aimed to evaluate the use of all-trans retinoic acid (ATRA)-loaded microneedle (MN) patches as a simple, alternative therapeutic option to traditional surgical treatments. This therapeutic strategy was designed to induce the proliferation of basal keratinocytes and accelerate stratum corneum turnover, leading to the lesion falling off the surface of the skin. The MN patch induced epidermal hyperplasia and marked expression of heparin-binding epidermal growth factor-like growth factor mRNA and protein corresponding to ATRA activity in the skin of HR-1 hairless mice. The acceleration of stratum corneum turnover was also observed by the dansyl chloride method. The skin irritation study in mice and safety study in humans support the safety findings of our study. Overall, MN patches can offer an effective and safe means of ATRA delivery into the skin, and the ATRA-loaded MN patch appears to be an effective pharmaceutical product providing a novel therapeutic option for seborrheic keratosis.