Immune-mediated changes in actinic keratosis following topical treatment with imiquimod 5% cream

Interferon and Toll-Like Receptor 7 Response in COVID-19: Implications of Topical Imiquimod for Prophylaxis and Treatment

BACKGROUND

The innate immune system is recognized as an essential aspect of COVID-19 pathogenesis. Toll-like receptors (TLRs) are important in inducing antiviral response, triggering downstream production of interferons (IFNs). Certain loss-of-function variants in TLR7 are associated with increased COVID-19 disease severity, and imiquimod (ImiQ) is known to have immunomodulating effects as an agonist of TLR7. Given that topical imiquimod (topImiQ) is indicated for various dermatologic conditions, it is necessary for dermatologists to understand the interplay between innate immunity mechanisms and the potential role of ImiQ in COVID-19, with a particular focus on TLR7.

SUMMARY

Our objective was to survey recent peer-reviewed scientific literature in the PubMed database, examine relevant evidence, and elucidate the relationships between IFNs, TLR7, the innate immune system, and topImiQ in the context of COVID-19. Despite limited studies on this topic, current evidence supports the critical role of TLRs in mounting a strong immune response against COVID-19. Of particular interest to dermatologists, topImiQ can result in systemic upregulation of the immune system via activation of TLR7. Key Message: Given the role of TLR7 in the systemic activation of the immune system, ImiQ, as a ligand of the TLR7 receptor, may have potential therapeutic benefit as a topical immunomodulatory treatment for COVID-19.

Comparative study of imiquimod 3.75% vs. photodynamic therapy for actinic keratosis of the scalp

BACKGROUND/PURPOSE

To assess efficacy, tolerability, adverse effects, recurrence, and aesthetic results of imiquimod 3.75% vs. photodynamic therapy with 5-aminolaevulinic acid (MAL-PDT) for actinic keratosis (AK).

METHODS

A small randomized, intraindividual right-left pilot study for AK treatment of multiple scalp lesions was performed. Patients were treated with imiquimod and subsequently MAL-PDT (on opposite sides of the scalp) 14 days apart. Study end points were evaluated with clinical and dermoscopic examinations at 1, 3, 6, and 12 months.

RESULTS

Nine male bald patients were enrolled. Imiquimod achieved a slightly higher overall clearance rate than MAP-PDT (68.1% vs 56.5%). According to AK degree of severity, clearance rates were greater for degree I and III with imiquimod (68.8%, 64.5% and 75% with imiquimod vs. 48%, 69.8%, and 66.7% for MAL-PDT, respectively). At 12 months, a slightly higher total recurrence rate was noted for imiquimod compared with MAL-PDT (9.9% vs. 8.6%); new lesions were 2 degree I for imiquimod and 4 degree I for MAL-PDT. For both treatments, pain was moderate/strong (even if MAL-PDT seems to be less tolerable) adverse effects are common and transient; aesthetic results excellent.

CONCLUSION

Both imiquimod and MAL-PDT were effective in the reduction in the number of AK. In the long-term, both present a good effectiveness maintained over time with excellent aesthetic results. A combination or sequential therapy could optimize the management of the cancerization field.

Imiquimod - A toll like receptor 7 agonist - Is an ideal option for management of COVID 19

According to numerous recent publications, the COVID-19 patients have lymphopenia, higher infection-related biomarkers and several elevated inflammatory cytokines (i.e. tumor necrosis factor (TNF)-α, interleukin IL-2R and IL-6). The total number of B cells, T cells and NK cells are significantly decreased. RNA viruses, SARS-CoV-2 included, hit the innate immune system in order to cause infection, through TLRs 3, 7 and 8. Imiquimod is an immune-stimulator that activates TLR 7 and can be used to enhance the innate and adaptive immunity. Preclinical and clinical trials are proposed.

Long-term clinical outcomes of imiquimod 5% cream vs. diclofenac 3% gel for actinic keratosis on the face or scalp: a pooled analysis of two randomized controlled trials

BACKGROUND

Actinic keratosis (AK) is an early in situ epidermal cancer which can progress to invasive squamous cell carcinoma (SCC). Imiquimod 5% cream (IMIQ) and diclofenac 3% gel (DIC) are frequently used to treat AK; however, their long-term effects following repeated treatment cycles have never been compared.

OBJECTIVE

To compare IMIQ and DIC in the treatment of AK with respect to the risk of change to grade III AK or invasive SCC, after 3 years.

METHODS

Data were pooled from two randomized, active-controlled, open-label, multicentre, multinational, phase IV studies (Clinicaltrials.gov NCT00777127/NCT01453179), with two parallel groups. Studies were conducted between 2008 and 2015 and were almost identical in design. Patients eligible for inclusion were immunocompetent adults with 5-10 visible AK lesions on the face/scalp and grade I/II AK. The primary endpoint was inhibition of histological change to grade III AK or invasive SCC in the study treatment area, observed until month 36. Patients applied either IMIQ or DIC for a maximum of six treatment cycles.

RESULTS

In total, 479 patients (IMIQ 242; DIC 237) were included in the full analysis set. Histological change to grade III AK or invasive SCC was observed until month 36 in 13 (5.4%) patients treated with IMIQ, compared with 26 (11.0%) patients treated with DIC (absolute risk difference -5.6% [95% confidence interval -10.7%, -0.7%]). Time to histological change was greater in the IMIQ group than the DIC group (P = 0.0266). Frequency of progression to invasive SCC was lower with IMIQ than with DIC at all time points. Initial clearance rate was higher in the IMIQ group compared with the DIC group, while recurrence rate was lower. Both treatments were well tolerated.

CONCLUSIONS

Over 3 years, IMIQ was superior to DIC in clearing AK lesions and preventing histological change to grade III AK or invasive SCC and recurrence.

Actinic keratosis - review for clinical practice

Actinic keratosis (AK) is a lesion that arises as a result of excessive exposure to solar radiation and appearing predominantly on Fitzpatrick phototype I and II skin. Given that some AKs evolve into squamous cell carcinoma, these lesions are considered premalignant in nature, occurring mostly in elderly men and immunosuppressed individuals chronically exposed to ultraviolet (UV) radiation. There are several mechanisms for the formation of AKs; among them are oxidative stress, immunosuppression, inflammation, altered proliferation and dysregulation of cell growth, impaired apoptosis, mutagenesis, and human papillomavirus (HPV). Through the understanding of these mechanisms, several treatments have emerged. Among the options for AK treatment, the most commonly used include 5-fluorouracil (5-FU), cryotherapy, diclofenac, photodynamic therapy (PDT), imiquimod (IQ), retinoids, and ingenol mebutate (IM). There have been recent advances in the treatment options that have seen the emergent use of newer agents such as resiquimod, betulinic acid, piroxicam, and dobesilate. The combination between therapies has presented relevant results with intention to reduce duration of therapy and side effects. All AK cases must be treated because of their propensity to transform into malignancy and further complicate treatment. In addition to medical or surgical care, education about sun exposure prevention remains the best and most cost-effective method for AK prevention. The objective of this article is to conduct a literature review of the clinical presentation of AK including advances in treatment options available.

Therapeutic effect of imiquimod on dextran sulfate sodium-induced ulcerative colitis in mice

BACKGROUND

Imiquimod is a Toll-like receptor-7 agonist that regulates immunity and can be used as an immune adjuvant. Ulcerative colitis has a close correlation with immune disorder.

AIM

To investigate the therapeutic effect of imiquimod on dextran sulfate sodium (DSS)-induced colitis and explore the underlying mechanisms.

METHODS

C57BL/6J C57 mice received 3% DSS for 7 days to induce ulcerative colitis. Groups of mice were intraperitoneally injected with dexamethasone (DXM, 1.5 mg/kg) or imiquimod (IMQ, 30 mg/kg) at the same time daily. During the experimental period, clinical signs, body weight, stool consistency and visible fecal blood were monitored and recorded daily; colitis was evaluated by disease activity index (DAI) score and by histological score. At the conclusion of the experiment, the level of colonic myeloperoxidase (MPO) activity and the serum levels of the cytokines tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6) and interleukin 10 (IL-10) were measured.

RESULTS

Administration of 3% DSS for 7 days successfully induced acute colitis associated with diarrhea, bloody mucopurulent stool, body weight decreases, and other changes. Colitis severity was significantly ameliorated in the IMQ treatment groups, as determined by hematoxylin-eosin (HE) staining and histopathological scores. Moreover, IMQ significantly reduced the activity of MPO in colonic tissue and the serum levels of inflammatory cytokines, increased colon length and spleen weight, and effectively inhibited microscopic damage to the colon tissue.

CONCLUSION

IMQ had beneficial effects on DSS-induced ulcerative colitis, supporting its further development and clinical application in ulcerative colitis.

Drug therapy of advanced cutaneous squamous cell carcinoma: is there any evidence?

PURPOSE OF REVIEW

There are few randomized controlled studies to guide the treatment of advanced cutaneous squamous cell carcinoma. The existing treatments are mostly based on case reports and small case series. Here we review recently available insights concerning the treatment of locally advanced and metastatic squamous cell carcinoma, with a special emphasis on novel targeted therapy and immunotherapy.

RECENT FINDINGS

Surgery and combination of chemotherapy and radiation therapy have been long considered the gold standard options for advanced squamous cell carcinoma. The detection of clinically relevant driver mutations has opened the door to the use of novel targeted therapies. Recent studies have shown that aggressive cutaneous squamous cell carcinoma is characterized by a very high mutational background. Furthermore, the importance of the defective immunosurveillance in the growth of cutaneous squamous cell carcinoma and the critical role of programed cell death protein 1 and programmed death-ligand 1 interaction in skin tumor development provides a rationale for the use of immune checkpoint inhibitors.

SUMMARY

Epidermal growth factor receptor inhibitors have shown to have satisfactory antitumor activity with acceptable side-effect profile. However, their place in management of advanced cutaneous squamous cell carcinoma alone or in combination with either radiation therapy and/or chemotherapy needs to be better characterized. The available preliminary findings suggest that immune checkpoint inhibitors represent a potentially valuable alternative in cutaneous aggressive squamous cell carcinoma, promising a further expansion of their indication spectrum. Randomized controlled studies will allow us to better characterize their practical value.

Patient satisfaction and reported outcomes on the management of actinic keratosis

Actinic keratosis (AK) is a common dermatologic condition in which hyperplastic epidermal lesions develop in response to excessive and chronic exposure to ultraviolet (UV) radiation. If left untreated, AK can progress to squamous cell carcinomas of the skin. Incidence is rising worldwide as a result of the progressive aging of populations and an increase in lifetime cumulative exposure to UV radiation. Currently, various treatment options exist, which range from topical medications to light-based therapies and procedural modalities. In this article, we will review the treatment options for AK with a focus on assessments of patient satisfaction with treatment.

The toll-like receptor agonist imiquimod is active against prions

Using a yeast-based assay, a previously unsuspected antiprion activity was found for imiquimod (IQ), a potent Toll-like receptor 7 (TLR7) agonist already used for clinical applications. The antiprion activity of IQ was first detected against yeast prions [PSI⁺] and [URE3], and then against mammalian prion both ex vivo in a cell-based assay and in vivo in a transgenic mouse model for prion diseases. In order to facilitate structure-activity relationship studies, we conducted a new synthetic pathway which provides a more efficient means of producing new IQ chemical derivatives, the activity of which was tested against both yeast and mammalian prions. The comparable antiprion activity of IQ and its chemical derivatives in the above life forms further emphasizes the conservation of prion controlling mechanisms throughout evolution. Interestingly, this study also demonstrated that the antiprion activity of IQ and IQ-derived compounds is independent from their ability to stimulate TLRs. Furthermore, we found that IQ and its active chemical derivatives inhibit the protein folding activity of the ribosome (PFAR) in vitro.

A combination of local inflammation and central memory T cells potentiates immunotherapy in the skin

Adoptive T cell therapy uses the specificity of the adaptive immune system to target cancer and virally infected cells. Yet the mechanism and means by which to enhance T cell function are incompletely described, especially in the skin. In this study, we use a murine model of immunotherapy to optimize cell-mediated immunity in the skin. We show that in vitro-derived central but not effector memory-like T cells bring about rapid regression of skin-expressing cognate Ag as a transgene in keratinocytes. Local inflammation induced by the TLR7 receptor agonist imiquimod subtly yet reproducibly decreases time to skin graft rejection elicited by central but not effector memory T cells in an immunodeficient mouse model. Local CCL4, a chemokine liberated by TLR7 agonism, similarly enhances central memory T cell function. In this model, IL-2 facilitates the development in vivo of effector function from central memory but not effector memory T cells. In a model of T cell tolerogenesis, we further show that adoptively transferred central but not effector memory T cells can give rise to successful cutaneous immunity, which is dependent on a local inflammatory cue in the target tissue at the time of adoptive T cell transfer. Thus, adoptive T cell therapy efficacy can be enhanced if CD8(+) T cells with a central memory T cell phenotype are transferred, and IL-2 is present with contemporaneous local inflammation.

Molecular diagnostic strategies: a role in the practice of dermatology

Molecular diagnostic strategies are gaining wider acceptance and use in dermatology and dermatopathology as more practitioners in this field develop an understanding of the principles and applications of genomic technologies. Molecular testing is facilitating more accurate diagnosis, staging, and prognostication, in addition to guiding the selection of appropriate treatment, monitoring of therapy, and identification of novel therapeutic targets, for a wide variety of skin diseases.

Roles of the immune system in skin cancer

Over the past several decades, there has been increasing interest in understanding the roles of the immune system in the development and progression of cancer. The importance of the immune system in human skin cancer has been long recognized based primarily upon the increased incidence of skin cancers in organ transplant recipients and mechanisms of ultraviolet (UV) radiation-mediated immunomodulation. In this review, we integrate multiple lines of evidence highlighting the roles of the immune system in skin cancer. First, we discuss the concepts of cancer immunosurveillance and immunoediting as they might relate to human skin cancers. We then describe the clinical and molecular mechanisms of skin cancer development and progression in the contexts of therapeutic immunosuppression in organ transplant recipients, viral oncogenesis, and UV radiation-induced immunomodulation with a primary focus on basal cell carcinoma and squamous cell carcinoma. The clinical evidence supporting expanding roles for immunotherapy is also described. Finally, we discuss recent research examining the functions of particular immune cell subsets in skin cancer and how they might contribute to both antitumour and protumour effects. A better understanding of the biological mechanisms of cancer immunosurveillance holds the promise of enabling better therapies.

Immunomodulation by imiquimod in patients with high-risk primary melanoma

Imiquimod is a synthetic Toll-like receptor 7 (TLR7) agonist approved for the topical treatment of actinic keratoses, superficial basal cell carcinoma, and genital warts. Imiquimod leads to an 80–100% cure rate of lentigo maligna, but studies of invasive melanoma are lacking. We conducted a pilot study to characterize the local, regional, and systemic immune responses induced by imiquimod in patients with high-risk melanoma. After treatment of the primary melanoma biopsy site with placebo or imiquimod cream, we measured immune responses in the treated skin, sentinel lymph nodes (SLN), and peripheral blood. Treatment of primary melanomas with 5% imiquimod cream was associated with an increase in both CD4+ and CD8+ T cells in the skin, and CD4+ T cells in the SLN. Most of the CD8+ T cells in the skin were CD25 negative. We could not detect any increases in CD8+ T cells specifically recognizing HLA-A*0201-restricted melanoma epitopes in the peripheral blood. The findings from this small pilot study demonstrate that topical imiquimod treatment results in enhanced local and regional T cell numbers in both the skin and SLN. Further research into TLR7 immunomodulating pathways as a basis for effective immunotherapy against melanoma in conjunction with surgery is warranted.

TLR7 enables cross-presentation by multiple dendritic cell subsets through a type I IFN-dependent pathway

Conjugation of TLR agonists to protein or peptide antigens has been demonstrated in many studies to be an effective vaccine formula in inducing cellular immunity. However, the molecular and cellular mediators involved in TLR-induced immune responses have not been carefully examined. In this study, we identify Type I IFN and IL-12 as critical mediators of cross-priming induced by a TLR7 agonist-antigen conjugate. We demonstrate that TLR7-driven cross-priming requires both Type I IFN and IL-12. Signaling through the IFN-αβR was required for the timely recruitment and accumulation of activated dendritic cells in the draining lymph nodes. Although IL-12 was indispensable during cross-priming, it did not regulate DC function. Therefore, the codependency for these 2 cytokines during TLR7-induced cross-priming is the result of their divergent effects on different cell-types. Furthermore, although dermal and CD8α(+) DCs were able to cross-prime CD8(+) T cells, Langerhans cells were unexpectedly found to potently cross-present antigen and support CD8(+) T-cell expansion, both in vitro and in vivo. Collectively, the data show that a TLR7 agonist-antigen conjugate elicits CD8(+) T-cell responses by the coordinated recruitment and activation of both tissue-derived and lymphoid organ-resident DC subsets through a Type I IFN and IL-12 codependent mechanism.

Imiquimod 3.75% cream (Zyclara) for the treatment of actinic keratoses

INTRODUCTION

actinic keratosis is a premalignant disease with a high incidence and is a strong predictor for the development of squamous cell carcinoma. Various treatment options have been established over recent years, including topical treatment with imiquimod, 5-fluorouracil, diclofenac or photodynamic therapy, cryotherapy and surgical procedures.

AREAS COVERED

this review covers basic and clinical experiences with imiquimod 3.75% for topical treatment of actinic keratosis of the face and balding scalp and its comparators with special focus on imiquimod 5%. It also covers pharmacology of imiquimod 3.5% and its contribution to the current treatment options of actinic keratoses.

EXPERT OPINION

imiquimod 3.75% is an interesting, safe and well-tolerated treatment option for actinic keratoses of the face or balding scalp especially in respect of compliance, as it is indicated for daily use for a shorter time period (2 times, 2-week cycles) and approved for use on larger areas compared with imiquimod 5%. Data from current trials indicate lower efficacy compared with imiquimod 5% cream when applied three times a week for 16 weeks or for two 4-week cycles with a 4-week no-treatment interval, but indicate similar efficacy when compared with a twice-weekly schedule for 16 weeks. An additive effect was observed when combining cryosurgery followed by imiquimod 3.75%.

Reduction in cisplatin genotoxicity (micronucleus formation) in non target cells of mice by protransfersome gel formulation used for management of cutaneous squamous cell carcinoma

Cisplatin-loaded protransfersome system was prepared and characterized for in vitro drug permeation, drug deposition and antitumor effect. A histopathological study and a genotoxicity study were also done. The skin permeation data of cisplatin from protransfersome gel formulation revealed 494.33 ± 11.87 μg cm-2, which was significantly higher than that from the control plain drug solution in 0.9 % NaCl (p < 0.001). Untreated group of animals showed invasive moderately differentiated keratinizing squamous cell carcinoma (malignant stage). However, with cisplatin loaded protransfersome gel system simple epithelial hyperplasia (pre-cancerous stage) with no cancerous growth was observed. Also, a significant induction in micronucleus formation was found in the group that was treated with injectable intraperitoneal cisplatin preparation in 0.9 % saline as compared to the group treated with topical protransfersome gel formulation. The findings of this research work appear to support improved, site-specific and localized drug action in the skin, thus providing a better option for dealing with skin related problems like squamous cell carcinoma.

Current and emerging treatment strategies for the treatment of actinic keratosis

Actinic keratoses are encountered by physicians worldwide on a daily basis. As these precancerous lesions can transform to skin carcinomas, it is important to understand the many available options to use as treatment. In recent years, new therapeutic options have emerged to treat this common condition. These treatments as well as a review of the literature of conventional therapies will be discussed.

Imiquimod 2.5% and 3.75% for the treatment of actinic keratoses: results of two placebo-controlled studies of daily application to the face and balding scalp for two 3-week cycles

BACKGROUND

Imiquimod 5% cream is approved as a 16-week regimen for the treatment of actinic keratoses involving a 25-cm(2) area of skin.

OBJECTIVE

We sought to evaluate imiquimod 2.5% and 3.75% creams for short-course treatment of the entire face and scalp.

METHODS

In two identical studies, adults with 5 to 20 lesions were randomized to placebo, or imiquimod 2.5% or 3.75% cream (1:1:1). Up to two packets (250 mg each) were applied per dose once daily for two 3-week treatment cycles, with a 3-week, no-treatment interval. Efficacy was assessed at 8 weeks posttreatment.

RESULTS

In all, 490 subjects were randomized to placebo, or imiquimod 2.5% or 3.75% cream. Median baseline lesion counts for the treatment groups were 9 to 10. Complete and partial clearance rates were 5.5% and 12.8% for placebo, 25.0% and 42.7% for imiquimod 2.5%, and 34.0% and 53.7% for imiquimod 3.75% (P < .001, each imiquimod vs placebo; P = .034, 3.75% vs 2.5% for partial clearance). Median reductions from baseline in lesion count were 23.6%, 66.7%, and 80.0% for the placebo, imiquimod 2.5%, and imiquimod 3.75% groups, respectively (P < .001 each imiquimod vs placebo). There were few treatment-related discontinuations. Temporary treatment interruption (rest) rates were 0%, 17.1%, and 27.2% for the placebo, imiquimod 2.5%, and imiquimod 3.75%, respectively.

LIMITATIONS

Local effects of imiquimod, including erythema, may have led to investigator and subject bias.

CONCLUSIONS

Both imiquimod 2.5% and 3.75% creams were more effective than placebo and had an acceptable safety profile when administered daily as a 3-week on/off/on regimen.

Safety and Efficacy of Multiple 16-week Courses of Topical Imiquimod for the Treatment of Large Areas of Skin Involved with Actinic Keratoses

OBJECTIVE

Safety of multiple 16-week courses of imiquimod applied to large areas (>25 cm(2)) of skin with actinic keratoses.

DESIGN

Subjects applied 1 to 6 packets two times per week for 16 weeks; if actinic keratoses were persistent at two months post-treatment, up to two additional courses could be administered within the 18-month study period.

SETTING

Multicenter, outpatient.

PARTICIPANTS

Adults with >/=4 actinic keratoses on the head, torso, and/or extremities.

MEASUREMENTS

Treatment discontinuations, adverse events, lesion counts.

RESULTS

Safety analyses included 551 subjects. At baseline, mean overall treatment area was 625+/-1114cm(2). Overall, the mean days on study was 467+/-157, and the mean exposure 215+/-133 packets with 155, 150, and 250 subjects receiving 1, 2, or 3 treatment courses, respectively. Of the 155 subjects (28.1%) who did not complete the study, 20 (3.6%) and 9 (1.6%) were discontinued for adverse events and local skin reactions, respectively. Adverse events related to study drug were reported by 40.5 percent of subjects. The local skin reactions rated as severe reported by the most subjects were erythema (31.4%), flaking/scaling/drying (23.8%), and scabbing/crusting (22.0%). For 525 subjects with analyzable lesion data, the mean baseline lesion count was 45.5+/-2.4. Overall reduction in target lesion count was 80.2 percent (p<0.0001, 95% CI 77.2-83.3%), with overall complete clearance rate of 36.4 percent and partial clearance rate (>/=75% reduction) of 68.6 percent.

CONCLUSION

Multiple 16-week courses of imiquimod to treat actinic keratoses were well tolerated and significantly decreased lesions in subjects with extensive actinic keratoses.

The immunologic aspects of poxvirus oncolytic therapy

The concept of using replicating oncolytic viruses in cancer therapy dates to the beginning of the twentieth century. However, in the last few years, an increasing number of pre-clinical and clinical trials have been carried out with promising preliminarily results. Novel, indeed, is the suggestion that viral oncolytic therapy might not operate exclusively through an oncolysis-mediated process but additionally requires the "assistance" of the host's immune system. Originally, the host's immune response was believed to play a predominant obstructive role against viral replication, hence limiting the anti-tumor efficacy of viral vectors. Recent data, however, suggest that the immune response may also play a key role in promoting tumor destruction in association with the oncolytic process. In fact, immune effector pathways activated during oncolytic virus-induced tumor rejection seem to follow a similar pattern to those observed when the broader phenomenon of immune-mediated tissue-specific rejection occurs in other immune-related pathologies. We recently formulated the "Immunologic Constant of Rejection" hypothesis, emphasizing commonalties in transcriptional patterns observed when tissue-destruction occurs: whether with a favorable outcome, such as in tumor rejection and pathogen clearance; or a destructive one, such as in allograft rejection or autoimmunity. Here, we propose that a similar mechanism induces clearance of virally infected tumors and that such a mechanism is primarily dependent on innate immune functions.

First in human phase I trial of 852A, a novel systemic toll-like receptor 7 agonist, to activate innate immune responses in patients with advanced cancer

PURPOSE

Recent advances in the understanding of innate immunity suggest that an orchestrated sequence of events is required to elicit a productive immune response against cancer. We studied the systemic administration of the Toll-like receptor 7 agonist 852A, a small-molecule imidazoquinoline, in patients with advanced cancer. Preclinical studies showed that 852A stimulates plasmacytoid dendritic cells to produce multiple cytokines, such as IFN-alpha, interleukin-1 receptor antagonist, and IFN-inducible protein-10. Our goal was to define the tolerated dose, pharmacokinetics, pharmacodynamics, and immunologic effects of 852A in humans.

EXPERIMENTAL DESIGN

Eligible adult patients with refractory solid organ tumors received i.v. 852A thrice weekly for 2 weeks. Patients who had responses or stable disease were eligible for additional cycles.

RESULTS

Twenty-five patients (median age, 55.0 years; 72% male) were enrolled in six cohorts at dose levels of 0.15 to 2.0 mg/m(2). Serum drug levels showed dose proportionality and no evidence of drug accumulation. The maximum tolerated dose was 1.2 mg/m(2); higher doses were limited by fatigue and constitutional symptoms. Increases in IFN-alpha, interleukin-1 receptor antagonist, and IFN-inducible protein-10, immunologic activity, and clinical symptoms were observed in all patients receiving dose levels > or =0.6 mg/m(2). Significant correlations were found between pharmacodynamic biomarkers and pharmacokinetic variables, and an objective clinical response was seen.

CONCLUSIONS

852A was safely administered i.v. at doses up to 1.2 mg/m(2) thrice weekly for 2 weeks with transient or reversible adverse effects. This novel Toll-like receptor 7 agonist is biologically active and holds promise for stimulating innate immune responses. Future trials are warranted to assess its therapeutic role in patients with cancer.

Cutaneous pharmacodynamics of a toll-like receptor 7 agonist, 852A, in humans

852A is a specific toll-like receptor 7 (TLR7) agonist. Thirty-two healthy adults (8 subjects per group) received two 1-g topical applications over 400 cm(2), separated by >or= 5 days, of 852A 0.01% followed by vehicle, vehicle followed by 852A 0.1%, 852A 0.3% followed by vehicle, or vehicle followed by 852A 1.0%. Systemic absorption was minimal as 852A was not quantifiable in any serum sample up to 24 hours postadministration and was only quantifiable at 24 hours in the urine of 4 of 8 subjects after application of 852A 1.0%. No systemic adverse events were associated with drug treatment. Gene expression analysis from application site biopsies showed a >or=2-fold increase in expression for 40 genes in at least 2 subjects. CXCL9/MIG (8/32 subjects), CCL2/MCP1 (7/32), and OAS3 (5/32) were most frequently increased, followed by other type I interferon-inducible genes. Cluster analysis of the genes with a >or=2-fold increase did not reveal a definitive pattern with respect to 852A concentration or time of biopsy. Overall, single topical application of 852A up to 1.0% was well tolerated. Data gathered from these subjects are suggestive that 852A can produce increases in local gene expression consistent with TLR7 stimulation.

Transcriptional networks in plasmacytoid dendritic cells stimulated with synthetic TLR 7 agonists

Background

Plasmacytoid Dendritic Cells (pDC) comprise approximately 0.2 to 0.8% of the blood mononuclear cells and are the primary type 1 interferon (IFN), producing cells, secreting high levels of IFN in response to viral infections. Plasmacytoid dendritic cells express predominantly TLRs 7 & 9, making them responsive to ssRNA and CpG DNA. The objective of this study was to evaluate the molecular and cellular processes altered upon stimulation of pDC with synthetic TLR 7 and TLR 7/8 agonists. To this end, we evaluated changes in global gene expression upon stimulation of 99.9% pure human pDC with the TLR7 selective agonists 3M-852A, and the TLR7/8 agonist 3M-011.

Results

Global gene expression was evaluated using the Affymetrix U133A GeneChip^® and selected genes were confirmed using real time TaqMan^® RTPCR. The gene expression profiles of the two agonists were similar indicating that changes in gene expression were solely due to stimulation through TLR7. Type 1 interferons were among the highest induced genes and included IFNB and multiple IFNα subtypes, IFNα2, α5, α6, α8, α1/13, α10, α14, α16, α17, α21. A large number of chemokines and co-stimulatory molecules as well as the chemokine receptor CCR7 were increased in expression indicating maturation and change in the migratory ability of pDC. Induction of an antiviral state was shown by the expression of several IFN-inducible genes with known anti-viral activity. Further analysis of the data using the pathway analysis tool MetaCore gave insight into molecular and cellular processes impacted. The analysis revealed transcription networks that show increased expression of signaling components in TLR7 and TLR3 pathways, and the cytosolic anti-viral pathway regulated by RIG1 and MDA5, suggestive of optimization of an antiviral state targeted towards RNA viruses. The analysis also revealed increased expression of a network of genes important for protein ISGylation as well as an anti-apoptotic and pro-survival gene expression program.

Conclusion

Thus this study demonstrates that as early as 4 hr post stimulation, synthetic TLR7 agonists induce a complex transcription network responsible for activating pDC for innate anti-viral immune responses with optimized responses towards RNA viruses, increased co-stimulatory capacity, and increased survival.

Complexities of targeting innate immunity to treat infection

Innate immunity is an ancient form of host defence that is activated rapidly to enable, through a multiplicity of effector mechanisms, defence against a broad spectrum of microbial threats. From this perspective, innate immunity has desirable characteristics of a therapy against infections, and, as a consequence, the innate immune system has become a major target for the development of therapeutics to control inflammation and immune defences. Although advances in the field have come at a furious pace, and several companies are advancing the first Toll-like receptor-based drugs, there remain many unanswered questions about innate immunity and maintaining balance in the immune response. Indeed, innate immunity represents an enormously complex network of molecules, pathways and interactions, controlled by multiple positive and negative regulatory proteins, which are starting to be evaluated in more depth using systems biology approaches. However, accompanying the protective mechanisms is the production of pro-inflammatory cytokines such that, if excessive amplification of innate immunity occurs, there is the potential for such syndromes as sepsis and chronic inflammation.

Sequential gene profiling of basal cell carcinomas treated with imiquimod in a placebo-controlled study defines the requirements for tissue rejection

An analysis of basal cell carcinoma subjected to local application of imiquimod revealed that most transcripts stimulated by imiquimod involve the activation of cellular innate and adaptive immune-effector mechanisms.

Background

Imiquimod is a Toll-like receptor-7 agonist capable of inducing complete clearance of basal cell carcinoma (BCC) and other cutaneous malignancies. We hypothesized that the characterization of the early transcriptional events induced by imiquimod may provide insights about immunological events preceding acute tissue and/or tumor rejection.

Results

We report a paired analysis of adjacent punch biopsies obtained pre- and post-treatment from 36 patients with BCC subjected to local application of imiquimod (n = 22) or vehicle cream (n = 14) in a blinded, randomized protocol. Four treatments were assessed (q12 applications for 2 or 4 days, or q24 hours for 4 or 8 days). RNA was amplified and hybridized to 17.5 K cDNA arrays. All treatment schedules similarly affected the transcriptional profile of BCC; however, the q12 × 4 days regimen, associated with highest effectiveness, induced the most changes, with 637 genes unequivocally stimulated by imiquimod. A minority of transcripts (98 genes) confirmed previous reports of interferon-α involvement. The remaining 539 genes portrayed additional immunological functions predominantly involving the activation of cellular innate and adaptive immune-effector mechanisms. Importantly, these effector signatures recapitulate previous observations of tissue rejection in the context of cancer immunotherapy, acute allograft rejection and autoimmunity.

Conclusion

This study, based on a powerful and reproducible model of cancer eradication by innate immune mechanisms, provides the first insights in humans into the early transcriptional events associated with immune rejection. This model is likely representative of constant immunological pathways through which innate and adaptive immune responses combine to induce tissue destruction.