A phase I clinical trial of imiquimod, an oral interferon inducer, administered daily

A single naturally occurring 2'-O-methylation converts a TLR7- and TLR8-activating RNA into a TLR8-specific ligand

TLR7 and TLR8 recognize RNA from pathogens and lead to subsequent immune stimulation. Here we demonstrate that a single naturally occurring 2’-O-methylation within a synthetic 18s rRNA derived RNA sequence prevents IFN-α production, however secretion of proinflammatory cytokines such as IL-6 is not impaired. By analysing TLR-deficient plasmacytoid dendritic cells and performing HEK293 genetic complementation assays we could demonstrate that the single 2’-O-methylation containing RNA still activated TLR8 but not TLR7. Therefore this specific 2’-O-ribose methylation in rRNA converts a TLR7 / TLR8 ligand to an exclusively TLR8-specific ligand. Interestingly, other modifications at this position such as 2’-O-deoxy or 2’-fluoro had no strong modulating effect on TLR7 or TLR8 activation suggesting an important role of 2’-O-methylation for shaping differential TLR7 or TLR8 activation.

Prolonged subcutaneous administration of 852A, a novel systemic toll-like receptor 7 agonist, to activate innate immune responses in patients with advanced hematologic malignancies

The toll-like receptor (TLR) 7 agonist 852A, a small-molecule imidazoquinoline, stimulates plasmacytoid dendritic cells to produce multiple cytokines. We conducted a Phase II study of 852A in patients with recurrent hematologic malignancies. The primary objective was assessing the activity of 852A administered subcutaneously twice weekly for 12 weeks. Secondary objectives were assessing the safety of 852A and its ability to activate the immune system with prolonged dosing. Patients with relapsed hematologic malignancies of any age with adequate organ function were eligible. Patients initiated dosing at 0.6 mg/m(2) twice weekly and escalated by 0.2 mg/m(2) after every two doses as tolerated to a target dose of 1.2 mg/m(2) . Patients with responses or stable disease were eligible for additional cycles. Seventeen patients (15 males) entered the study: 6 with AML, 5 ALL, 4 NHL, 1 Hodgkin's lymphoma, and 1 multiple myeloma. The mean age was 41 years (12-71 years). The median number of prior chemotherapy regimens was 5 (range = 1-14). Thirteen patients completed all 24 injections. Grade 3-4 toxicities included nausea, dyspnea, fever, myalgia, malaise, and cough. Responses included one complete response (ALL), one partial response (AML), two stable disease (AML and NHL), and 9 progressive disease. This is the first in-human hematologic malignancy trial of a subcutaneously (SC) delivered TLR7 agonist using a prolonged dosing schedule. 852A was safely administered up to 1.2 mg/m(2) twice weekly with evidence of sustained tolerability and clinical activity in hematologic malignancies. Systemic TLR agonists for the treatment of hematologic malignancies warrant further study.

The pharmacokinetics of Toll-like receptor agonists and the impact on the immune system

Toll-like receptor (TLR) ligation activates both the innate and adaptive immune systems, and plays an important role in antiviral and anti-tumor immunity. Therefore, a significant amount of effort has been devoted to exploit the therapeutic potential of TLR agonists. Depending on the therapeutic purpose, either as adjuvants to vaccine, chemotherapy or standalone therapy, TLR agonists have been administered via different routes. Both preclinical and clinical studies have suggested that the route of administration has significant effects on pharmacokinetics, and that understanding these effects is critical to the success of TLR agonist drug development. This article will summarize the pharmacokinetics of TLR agonists with different administration routes, with an emphasis on clinical studies of TLR ligands in oncologic applications.

Toll-like receptor-7 ligand Imiquimod induces type I interferon and antimicrobial peptides to ameliorate dextran sodium sulfate-induced acute colitis

BACKGROUND

The pathogenesis of inflammatory bowel disease (IBD) is associated with a dysregulated mucosal immune response. Certain stimulators of innate immunity (CpG DNA or GM-CSF) are reported to be anti-inflammatory in IBD. Toll-like receptor-7 (TLR7) is an important regulator of innate immunity and its activation plays a key role in induction of type I interferon (IFN). The present study tests the hypothesis that the TLR7 agonists Imiquimod has therapeutic efficacy in IBD.

METHODS

Acute colitis was induced in Balb/c mice by giving 5% dextran sodium sulfate (DSS) in drinking water for 7 days. Mice were treated with Imiquimod either orally or topically and its therapeutic effects on disease activity were examined. Isolated mouse CD11c+ dendritic cells and human intestinal epithelial cells (HT29, HCT116) were treated with Imiquimod (10 μg/mL) and their susceptibility to intracellular Salmonella typhimurium infection was assessed by gentamicin protection assay.

RESULTS

Oral administration of Imiquimod induced type I IFN expression in the gastrointestinal mucosa and ameliorated DSS-induced acute colitis as assessed by clinical parameters, histology, and mRNA expression of proinflammatory cytokines. Topical administration of Imiquimod also ameliorated DSS colitis by inducing the expression of type I IFN in the colonic mucosa. However, no evidence for a systemic IFN response was observed. Imiquimod treatments to both CD11c+ and intestinal epithelial cells significantly increased expression of antimicrobial peptides (AMPs) and reduced survival of intracellular S. typhimurium.

CONCLUSIONS

Imiquimod induces type I IFN and AMP to ameliorate DSS-induced acute colitis and prevents Salmonella survival. Therefore, Imiquimod treatments provide a new therapeutic approach for IBD patients.

Lipid-derived nanoparticles for immunostimulatory RNA adjuvant delivery

The specific activation of Toll-like receptors (TLRs) has potential utility for a variety of therapeutic indications including antiviral immunotherapy and as vaccine adjuvants. TLR7 and TLR 8 may be activated by their native ligands, single-stranded RNA, or by small molecules of the imidazoquinoline family. However the use of TLR7/8 agonists for in vivo therapy is limited by instability, in the case of RNA, or systemic biodistribution and toxicity in the case of small molecule agonists. We hypothesized that unique lipid-like materials, termed "lipidoids," could be designed to efficiently deliver immunostimulatory RNA (isRNA) to TLR-expressing cells to drive innate and adaptive immune responses. A library of lipidoids was synthesized and screened for the ability to induce type I IFN activation in human peripheral blood mononuclear cells when combined with isRNA oligonucleotides. Effective lipidoid-isRNA nanoparticles, when tested in mice, stimulated strong IFN-α responses following subcutaneous injection, had robust antiviral activity that suppressed influenza virus replication, and enhanced antiovalbumin humoral and cell-mediated responses when used as a vaccine adjuvant. Further, we demonstrate that whereas all immunological activity was MyD88-dependent, certain materials were found to engage both TLR7-dependent and TLR7-independent activity in the mouse suggestive of cell-specific delivery. These lipidoid formulations, which are materials designed specifically for delivery of isRNA to Toll-like receptors, were superior to the commonly used N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate-RNA delivery system and may provide new tools for the manipulation of TLR responses in vitro and in vivo.

Pharmacokinetics of daily self-application of imiquimod 3.75% cream in adult patients with external anogenital warts

Imiquimod 3.75% cream is a new formulation intended for daily self-application. The objective of this study was to characterize serum imiquimod pharmacokinetics under maximal use conditions. Adults with ≥8 warts or total wart area ≥100 mm² applied up to 1 packet of imiquimod 3.75% cream (250 mg cream, 9.375 mg imiquimod) once daily for 3 weeks. Blood was obtained prior to doses 1, 7, 14, and 21 and at selected time points after doses 1 and 21. Eighteen patients (13 men and 5 women) with a median wart count of 16 and total wart area of 60 mm² were enrolled. Day 21 mean (SD) serum C(max) was 0.49 (0.37) ng/mL, AUC₀₋₂₄ 6.80 (3.59) ng·h/mL, and t(1/2) 24.1 (12.4) hours. Steady state was achieved by day 7 with ~2-fold increase in C(max) and AUC after multiple dosing. Overall, C(max) was higher and t(max) shorter in women, with comparable AUC₀₋₂₄. Imiquimod metabolites were sporadically quantifiable. No patients discontinued for adverse events; 1 interrupted dosing for an application site ulcer. Treatment-related adverse events occurred in 16.7% of the patients. In conclusion, serum imiquimod concentrations were low after daily self-application to external anogenital warts of up to 1 packet of imiquimod 3.75% cream for 21 days.

Randomised clinical trial: anti-viral activity of ANA773, an oral inducer of endogenous interferons acting via TLR7, in chronic HCV

BACKGROUND

The ANA773 is an oral prodrug of a small-molecule toll-like receptor (TLR)7 agonist. Preclinical and healthy volunteer clinical studies with ANA773 have demonstrated induction of endogenous interferon-α (IFN-α) of multiple subtypes, which supports the potential utility in the treatment of chronic hepatitis C virus (HCV) infection.

AIM

To examine safety, tolerability, pharmacodynamics, pharmacokinetics and anti-viral activity of ANA773.

METHODS

The ANA773 was investigated in a double-blind, placebo-controlled study in 34 patients chronically infected with HCV of any genotype. Patients were treatment-naïve or had relapsed following previous interferon-based treatment. This dose escalation study was composed of four dose groups (800, 1200, 1600 and 2000mg). In each group, six to eight patients received ANA773 and two received placebo. Patients were dosed with ANA773 every-other-day for either 28 days (800, 1200 or 1600mg) or 10days (2000mg).

RESULTS

Mild to moderate adverse events were reported, with an increase in frequency and intensity with increasing dose. No serious AEs were reported and there were no early discontinuations. There were dose-related increases in various markers of IFN-α response. The mean maximum change in serum HCV RNA level from baseline was -0.34, -0.29, -0.40, -0.97 and -1.26log(10) in the placebo, 800, 1200, 1600 and 2000mg cohorts, respectively. At the 2000mg dose, ANA773 significantly (P=0.037) reduced serum HCV RNA levels (range: 0.14 to -3.10log(10) ).

CONCLUSION

The ANA773 was generally well tolerated and resulted in a dose-related IFN-dependent response leading to a significant decrease in serum HCV RNA levels in the 2000mg dose group.

TLR-based immune adjuvants

This work describes the nature and strength of the immune response induced by various Toll-like receptor ligands and their ability to act as vaccine adjuvants. It reviews the various ligands capable of triggering individual TLRs, and then focuses on the efficacy and safety of those agents for which clinical results are available.

Evaluation of imiquimod for topical treatment of vaccinia virus cutaneous infections in immunosuppressed hairless mice

Imiquimod is an immune response modifier prescribed as a topical medication for a number of viral and neoplastic conditions. We evaluated the antiviral activity of imiquimod against vaccinia virus (WR strain) cutaneous infections in immunosuppressed (with cyclophosphamide) hairless mice when administered after virus exposure. Primary lesions progressed in severity, satellite lesions developed, and infection eventually killed the mice. Once daily topical treatment with 1% imiquimod cream for 3, 4, or 5 days were compared to twice daily topical treatment with 1% cidofovir cream for 7 days. Survival time of mice in all treated groups was significantly prolonged compared to placebo controls. The mean day of death for the placebo group, 3-day imiquimod, 4-day imiquimod, 5-day imiquimod, and cidofovir groups were 15.5, 20.0, 20.5, 19.5, and 20.5 days post-infection, respectively. All treatment groups showed significant reductions in primary lesion size and in the number of satellite lesions. The cidofovir and 4-day imiquimod treatments delayed the appearance of lung virus titers by 3 and 6 days, respectively, although cutaneous lesion and snout virus titers were not as affected by treatment. Benefits in survival and lesion reduction were observed when imiquimod treatment was delayed from 24, 48, and 72 h post-infection. However, increasing the treatment dose of imiquimod from 1% to 5% led to a significant decrease in antiviral efficacy. These results demonstrate the protective effects of topically administered imiquimod against a disseminated vaccinia virus infection in this mouse model.

Plasmacytoid dendritic cell-derived type I interferon is crucial for the adjuvant activity of Toll-like receptor 7 agonists

There is a high demand for the development of adjuvants that induce cytotoxic T lymphocytes, which are crucial for the elimination of intracellular pathogens and tumor cells. Toll-like receptor (TLR) agonists are prime candidates to fulfill this role because they induce innate immune activation and promote adaptive immune responses. The successful application of the TLR7 agonist R837 for treatment of basal cell carcinoma shows the potential for exploiting this pathway in tumor immunotherapy. Imidazoquinolines like R837 and stimulatory ssRNA oligonucleotides both trigger TLR7-mediated immune activation, but little is known about their comparative ability to promote immunity induction. We investigated differences in innate immune activation and adjuvant activity between the imidazoquinoline R848 and the ssRNA TLR7 agonist polyUs21. In contrast to R848, polyUs21 induced detectable levels of intracellular interferon-alpha (IFN-alpha) in plasmacytoid dendritic cells (PDCs). In immunization studies, only polyUs21 led to robust priming of type 1 T helper cells and cytotoxic T lymphocytes, and it was more efficient in inducing antitumor immunity than R848. Notably, exogenous IFN-alpha augmented the adjuvant activity of R848, whereas depletion of PDC abrogated the adjuvanticity of polyUs21. This study, therefore, identifies sufficient IFN-alpha production by PDC as an important determinant of vaccine efficacy.

Toll-like receptor 7 selective synthetic oligoribonucleotide agonists: synthesis and structure-activity relationship studies

We previously reported a novel class of stabilized immune-modulatory RNA (SIMRA) compounds that activates TLR8 or both TLR7 and TLR8 depending on the nucleotide composition and chemical modifications incorporated. In the present study, to identify TLR7-selective agonists, we designed and synthesized novel SIMRA compounds with varying sequence compositions substituting 7-deaza-G for natural guanosine and studied immune-stimulatory activity in cell-based assays and in vivo in mice. SIMRA compounds activated NF-kappaB in HEK293 cells expressing TLR7 and induced cytokine production in mouse spleen cells and human PBMCs and higher levels of IFN-alpha in human pDCs, which correlated with TLR7 activation. Subcutaneous administration of SIMRA compounds to mice increased serum cytokine levels. TLR knockout mouse studies showed that both TLR7 and MyD88 are required for activity of SIMRA compounds. The presence of a 5'-AA/CN (A > C and N = U/C/7-deaza-G) and/or C/AUU-3' (C > A) trinucleotide at the 5'- and 3'-ends of SIMRA compound along with a 5'-AN(1)N(2)UG1A-3' (N(1) = A/C; N(2) = U/C/7-deaza-G) or UG1AZ(1)G1Z(2)UU (Z(1) = A < C; Z(2) = C < A) motif confers TLR7 selectivity over other sequence compositions. In conclusion, we have designed and synthesized novel SIMRA compounds that selectively act as agonists of TLR7.

Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topical imiquimod 5% cream

Imiquimod is a topical immune response modifier and stimulator used in humans to treat a number of cutaneous neoplasms. This case report describes a cat with actinic keratoses and squamous cell carcinoma of the pinnae. The pinnal lesions were treated with topical 5% imiquimod three times per week. Treatment was discontinued after 82 days of therapy. Twelve weeks of topical imiquimod application resulted in clinical resolution of the pinnal lesions. Although no post-treatment biopsies were performed, there was no relapse of the pinnal lesions in 5 months of clinical follow-up. Expected side effects were limited to erythema, crusting, alopecia, and mild discomfort at the sites of application during the first 3 weeks of application. These results suggest that topical imiquimod, although unproven, might be a therapeutic option or adjunct to therapy for cats with actinic keratoses and squamous cell carcinoma, especially those cats for whom surgery and radiation therapy are not an option.

Regression of lymphomatous skin deposits in a chronic lymphocytic leukemia patient treated with the Toll-like receptor-7/8 agonist, imiquimod

The identification of clinically relevant, active immunomodulatory agents is important for developing immunotherapeutic approaches to chronic lymphocytic leukemia (CLL) and other B-cell lymphomas that are not curable with conventional chemotherapy. In this investigation, the imidazoquinoline Toll-like receptor (TLR)-7/8 agonist, imiquimod, was found to mediate the clearance of a lymphomatous skin lesion in a CLL patient. Imidazoquinolines also activated TLR-7/8 signaling pathways, resulting in increased expression of costimulatory molecules on circulating tumor cells. These observations extend the therapeutic spectrum of imiquimod to cutaneous B-cell lymphomas and suggest the use of TLR-7/8 agonists in CLL immunotherapy.

An exploratory study of systemic administration of the toll-like receptor-7 agonist 852A in patients with refractory metastatic melanoma

PURPOSE

A topical Toll-like receptor 7 (TLR7) agonist induces regression of cutaneous melanocytic neoplasms. We explored antitumor activity of a systemically administered TLR7 agonist, 852A, in patients with metastatic melanoma.

EXPERIMENTAL DESIGN

We undertook a phase II, multicenter, open-label study in patients with chemotherapy-refractory metastatic melanoma. Patients received i.v. 852A, starting at 0.6 mg/m(2) and increasing to 0.9 mg/m(2) based on tolerance, thrice per week for 12 weeks. Clinical response was determined by Response Evaluation Criteria in Solid Tumors. Immune effects of 852A were monitored by measuring serum type I IFN and IP-10 together with assessment of immune cell markers in peripheral blood.

RESULTS

Twenty-one patients were enrolled. Thirteen patients completed the initial 12-week treatment cycle, with two discontinuing for adverse events considered to be possibly related to study drug. Four (19%) patients had disease stabilization for >100 days. One patient had a partial remission after two treatment cycles, but progressed during the third. Dose-limiting toxicity was observed in two patients. Serum type I IFN and IP-10 increased in most patients on 852A administration. Serum type I IFN increases were greater after dosing with 852A 0.9 mg/m(2) than after 0.6 mg/m(2) (P = 0.009). The maximal increase in IP-10 compared with baseline correlated with the maximal increase in type I IFN (P = 0.003). In the eight patients with immune cell marker data, CD86 expression on monocytes increased significantly post-first dose (P = 0.007).

CONCLUSION

Intravenous 852A was well tolerated and induced systemic immune activation that eventually resulted in prolonged disease stabilization in some patients with stage IV metastatic melanoma who had failed chemotherapy.

Resiquimod and other immune response modifiers as vaccine adjuvants

Synthetic immune response modifiers, such as resiquimod, are Toll-like receptor 7 and 8 agonists that act as vaccine adjuvants, enhancing antigen-specific antibody production and skewing immunity towards a Th1 response. These compounds stimulate dendritic cells to secrete cytokines, upregulate costimulatory molecule expression and enhance antigen presentation to T cells. The compounds have demonstrated vaccine adjuvant properties in a number of animal models. The adjuvant effects can be enhanced by measures that allow the drug to stay localized with the vaccine without quickly entering the systemic circulation. Clinical studies demonstrate that topical application of resiquimod and analogs is safe and effective at activating the local immune response. For injection, resiquimod or a similar compound may need to be formulated to allow for local immune activation without induction of systemic cytokines.

The pharmacology of endosomal TLR agonists in viral disease

The discovery of endosomal TLRs (Toll-like receptors) and their natural ligands has accelerated efforts to exploit them for therapeutic benefit. Importantly, this was preceded by clinical exploration of agents now known to be endosomal TLR agonists. Clinical effects in viral disease have been reported with agonists of TLR3, TLR7, TLR7/8 and TLR9, and the TLR7 agonist imiquimod is marketed for topical use against warts, a papillomavirus disease. The observed pre-clinical and clinical profiles of agonists of each of these TLRs suggest induction of a multifaceted innate immune response, with biomarker signatures indicative of type 1 interferon induction. However, these agents differ in both their pharmaceutical characteristics and the cellular distribution of their target TLRs, suggesting that drugs directed to these targets will display differences in their overall pharmacological profiles.

Therapeutic use of Aldara in chronic myeloid leukemia

The potent clinical responses seen in patients with chronic myeloid leukemia (CML) after administration of donor-specific lymphocytes, as well as the correlation between the presence of antigen specific T cells and prolonged remission in these patients, suggests a role for the immunological control of CML. Here we propose Aldara™, a clinically used formulation of imiquimod, as an agent for augmenting immune responses to CML antigens. Our proposition is based upon 3 tenets: 1) Endogenous dendritic cells (DC) of CML patients, which are known to be derived from the malignant clone, express and present various leukemic antigens; 2) CML-antigen reactive T cell clones exist in the patient but in many situations are ineffectively stimulated to cause significant hematological responses; and 3) Antigen presentation by mature, activated DC, which endogenously express CML-antigens may endow the pre-existing ineffective T cell responses with ability to control CML progression. The practical use of Aldara™ as a localized activator of DC in the context of present day leukemic therapeutics, as well as various properties of this unique immune modulator will be discussed.

Synthesis and evaluation of 2-substituted 8-hydroxyadenines as potent interferon inducers with improved oral bioavailabilities

In order to create novel compounds which possess potent interferon (IFN) inducing activities with excellent oral bioavailabilities, a series of 8-hydroxyadenines, which have various alkoxy or alkylthio moieties at the adenine C(2)-position, were synthesized and evaluated. The introduction of hydrophobic groups was not considered to be effective for potentiating the IFN-inducing activity, but several compounds having hydrophilic groups were effective. Among the compounds tested, compound 13f induced IFN from the dosage of 0.03 mg/kg, which was approximately 100-fold more potent than that of Imiquimod, and showed an excellent oral bioavailability (F=40%) which was 10-fold improved over 5, a lead compound (F=4%).

Death receptor-independent apoptosis in malignant melanoma induced by the small-molecule immune response modifier imiquimod

Bypassing molecular mechanisms of apoptosis deficiency may be of great utility for the successful treatment of malignant tumors. We have discovered that imiquimod, a small-molecule immunomodulator, exerts rather tumor-selective direct pro-apoptotic activity in vivo and in vitro towards cutaneous metastases of malignant melanoma, an aggressive skin tumor. This pro-apoptotic activity was not detectable with resiquimod, a closely related structural analogue whose pro-inflammatory activity is even greater than that of imiquimod. Unresponsiveness of some melanoma metastases to imiquimod in vivo corresponded to resistance towards imiquimod-induced apoptosis in vivo and in vitro. At the molecular level, the pro-apoptotic activity of imiquimod was independent of membrane-bound death receptors, but depended on Bcl-2 expression as demonstrated by overexpression of Bcl-2 in melanoma cells. Imiquimod is the first topical compound with the potential to bypass molecular mechanisms of apoptosis deficiency, a concept that may be relevant for other tumors as well.

Psoriasis induced by topical imiquimod

We report the provocation of localized psoriasis at the sites of application of topical imiquimod, possibly evolving into a generalized flare. A patient with pre-existing psoriasis that had been stable for 14 years was treated with imiquimod 5% cream daily for 6 weeks to three superficial basal cell carcinomas. During treatment one of the lesions developed severe local skin reactions necessitating rest periods, and received only 18 applications in 6 weeks. The other two lesions were treated for all 42 days. Psoriasiform changes developed at all three application sites. Nine-and-a-half weeks after completing treatment the patient developed disseminated small psoriatic lesions. Other recognized triggers of psoriasis were not identified. The psoriasis resolved slowly with conventional treatment.

Synthesis and structure–Activity relationships of 2-Amino-8-hydroxyadenines as orally active interferon inducing agents

Recently, we have reported the 8-hydroxyadenine derivatives (2-4) as a novel class of interferon (IFN) inducing agents. In the present study, a series of 8-hydroxyadenines, which possess various amino moieties at the adenine C(2)-position, were synthesized and evaluated for their ability to induce endogenous IFN in comparison to the known active agent, Imiquimod. Among the compounds prepared, compound 9o possessing a 2-methoxyethylamino group at C(2)-position of adenine was found to exhibit potent IFN inducing activity in vivo. Compound 9o induced IFN from the dosage of 0.1 mg/kg, which was 30-fold potent than that of Imiquimod, and showed a good oral bioavailability (F=81%).

Synthesis and structure-activity relationships of 2-substituted-8-hydroxyadenine derivatives as orally available interferon inducers without emetic side effects

Recently we reported the adenine derivatives (2-4) as new interferon (IFN) inducers. In the present study, we conducted a detailed structure and activity relationship study of 4 and its related derivatives on IFN inducing activity. From this study, we found that compound 4 exhibited the most potent IFN inducing activity in vitro with a minimum effective concentration of 0.01 microM, and 4 also showed strong IFN-inducing activity at doses of more than 0.3mg/kg by oral administration in mice. This potency was 10-fold stronger than that of Imiquimod. Moreover, 4 did not cause emesis in ferrets even at doses as high as 10mg/kg, whereas, 80% of animals were emetic when orally administered with the same dose of Imiquimod. These results indicate that compound 4 is superior to Imiquimod with respect to efficacy and safety.

Inhibition of IgE production by the imidazoquinoline resiquimod in nonallergic and allergic donors

The aim of this study was to examine whether the immune modulator resiquimod, which belongs like imiquimod to the imidazoquinolines, is capable of influencing IgE synthesis. Peripheral blood mono-nuclear cells from normal donors and patients with atopic dermatitis and with seasonal allergic rhinitis were analyzed in the presence of resiquimod, anti-CD40+interleukin-4 stimulation for induction of IgE, and anti-CD40+interleukin-4 in the presence of resiquimod, respectively. Our data show that spontaneous IgE production was inhibited in the presence of resiquimod, which was strongest at 10 ng per ml in both groups of allergic patients. Inhibition of IgE production after anti-CD40+interleukin-4 stimulation in the presence of resiquimod (10 ng per ml) was comparable between all the groups. In normal donors median inhibition of IgE synthesis was 93%, in seasonal allergic rhinitis patients 77%, and in patients with atopic dermatitis 72%. In order to rule out antiproliferative effects of resiquimod, which might influence IgE production, we also studied proliferation of peripheral blood mononuclear cells from normal donors, which remained unchanged in the presence of resiquimod at 0.1-10 ng per ml but was inhibited at 100 or 1000 ng per ml. In search of possible mechanisms responsible for the observed inhibition of IgE production, we analyzed the expression and production of molecules that are known to modulate IgE production, namely CD23 and interferon-gamma. CD23 expression on B cells was lower in the presence of resiquimod (10 ng per ml) in anti-CD40+interleukin-4 stimulated cells, whereas interferon-gamma was strongly induced (4-6-fold) by resiquimod (10 ng per ml). Furthermore, by using neutralizing interferon-gamma monoclonal antibodies, we show that inhibition of IgE production occurred in an interferon-gamma-dependent manner. Taken together our results show that resiquimod is a potent modulator of IgE production in vitro in normal but also in allergic donors.

Treatment of primary limited cutaneous extramammary Paget's disease with topical imiquimod monotherapy: Two case reports

We present two cases of primary limited cutaneous perineal and genital extramammary Paget's disease (EMPD) that were successfully treated with imiquimod 5% cream. Clinical and histologic cure was confirmed after 7.5 to 12 weeks of monotherapy. Treatment-associated morbidity is minimal compared with more invasive therapies, and self-application by the patient improves convenience and appeal. Imiquimod may offer a minimally invasive and promising therapeutic option for the treatment of limited cutaneous EMPD. The diagnosis and management of EMPD and the current literature regarding imiquimod therapy are reviewed.

Treatment of external genital warts in men using 5% imiquimod cream applied three times a week, once daily, twice daily, or three times a day

BACKGROUND

Medical therapy for genital warts remains suboptimal. The topical interferon and cytokine inducer, imiquimod, has been proved effective for the treatment of external genital and perianal warts, but there is a substantial difference in the response rates between men and women. When 5% imiquimod cream is applied three times a week up to 16 weeks, approximately two thirds of women treated with imiquimod achieve complete clearance of genital warts, whereas only about one third of men clear completely.

GOAL

This study was undertaken to determine whether more frequent application of topical imiquimod cream would improve the rate of genital wart clearance in men.

STUDY DESIGN

A randomized treatment trial involving adult men with biopsy-proven genital warts was conducted at nine centers in the United States and Canada using four different application frequencies.

RESULTS

Complete clearance rates during the 16-week treatment period were as follows for the different imiquimod treatment frequencies: three times a week (35 %), once daily (28 %), twice daily (24%), and three times a day (27%)(P = 0.88). The four treatment groups all showed comparable reductions in the total lesion area, with a median of more than a 90% reduction in the lesion area by the end of treatment. There was a significant increase in the incidence and severity of local skin reactions including erythema, vesicle formation, ulceration, and excoriation as the dosing frequency increased from three times a week to three times a day.

CONCLUSIONS

In this study, the optimal dosage regimen was the approved three times a week regimen. More frequent application (up to three times a day) did not improve clearance and was associated with an increase in local adverse events.

Imiquimod 5% cream in the treatment of Bowen's disease

BACKGROUND

Large-diameter lesions of Bowen's disease at sites such as the shin may be difficult to treat surgically and may require alternate treatment modalities.

OBJECTIVE

We investigated whether imiquimod 5% cream, a topical immune response modifier that stimulates the production of interferon alfa and other cytokines, is an effective topical treatment for Bowen's disease.

METHODS

This was a phase II, open-label study in 16 patients, treating a single biopsy-proven plaque of Bowen's disease that was 1 cm or larger in diameter, with once-daily self-application of imiquimod 5% cream for 16 weeks. A biopsy was performed on the treated area 6 weeks after the end of treatment, with patient follow-up at 3 and 6 months. Lymphocyte CD4/CD8 ratios were analyzed in pretreatment and posttreatment biopsy specimens by immunophenotyping the lymphocytic infiltrate.

RESULTS

Sixteen patients with Bowen's disease lesions ranging from 1 to 5.4 cm in diameter (0.7-21.6 cm(2) in area) were treated. Fifteen of these lesions were on the legs, and one was on the shoulder. Fourteen of the 15 patients (93% per protocol analysis) had no residual tumor present in their 6-week posttreatment biopsy specimens. One patient died of unrelated intercurrent illness before a biopsy specimen could be obtained. The median CD4/CD8 lymphocyte ratio in pretreatment biopsy specimens was 2:1, and this was reversed to a median of 1:2.2 in the posttreatment specimens. Ten patients completed 16 weeks of treatment, but 6 patients ceased treatment early (between 4 and 8 weeks) because of local skin reactions.

CONCLUSION

Imiquimod 5% cream appears to be an effective treatment for Bowen's disease on the lower limbs. The 93% positive treatment response in biopsy-proven cases (excludes patient who died from an intercurrent illness who did not undergo a posttreatment biopsy) compares favorably with other current treatment modalities. The dosing schedule and length of treatment for Bowen's disease require further evaluation.

Human papillomavirus infections: epidemiology, pathogenesis, and host immune response

Human papillomaviruses (HPVs) are ubiquitous and often cause lesions on the skin that come to the attention of the dermatologist. Skin lesions, or warts, often occur on the hands or soles of the feet and can cause embarrassment or discomfort. Genital HPV infections are transmitted by sexual contact. Infections associated with some HPV types have a high risk of progressing to carcinoma. This review discusses the molecular biology and genetics of human papillomaviruses and provides an overview of the virology, pathology, clinical manifestations, and host immune response to infection.

Impaired antiviral response and alpha/beta interferon induction in mice lacking beta interferon

We have generated mice lacking the gene for beta interferon and report that they are highly susceptible to vaccinia virus infection. Furthermore, in cultured embryo fibroblasts, viral induction of alpha interferon and of 2-5A synthetase genes is impaired. We also show that beta interferon does not prime its own expression.

Topical imiquimod: a review of its use in genital warts

Imiquimod is a topically active immunomodulatory agent that is formulated as a 5% cream for application by the patient. It is the first agent of its class, the immune response modifiers, to be used in the treatment of genital warts. In immunocompetent patients with genital warts, imiquimod stimulates the production of interferon-alpha and various other cytokines, and has indirect antiviral activity. In randomised, double-blind, vehicle-controlled clinical trials, complete clearance of warts occurred in 37 to 50% of immunocompetent patients with genital warts treated with imiquimod 5% cream 3 times a week for up to 16 weeks; partial clearance of warts (defined as a reduction in wart area of > or = 50%) was observed in 76% of recipients of imiquimod 5% cream. Rates of complete or partial clearance of warts were significantly higher in patients who applied imiquimod 5% cream 3 times a week than in recipients of imiquimod 1% or vehicle cream, each applied 3 times a week. A between-gender difference in clinical response to imiquimod 5% cream has been reported, with female patients experiencing higher rates of complete clearance of warts than males. Recurrence(s) of > or = 1 wart occurred in 13 to 19% of immunocompetent patients in whom complete clearance of warts had been achieved with imiquimod 5% cream. Imiquimod 5% cream also shows some clearance of warts in immunosuppressed HIV-infected patients with genital warts. Preliminary results of a vehicle-controlled study showed that the rate of partial clearance of warts (defined as a reduction in baseline wart area of >50%) [38%] was significantly higher with imiquimod 5% cream than with vehicle cream; however, the rate of complete clearance was not significantly higher than with vehicle cream. Imiquimod 5% cream is generally well tolerated by immunocompetent and HIV-infected patients. Local skin reactions (mainly mild or moderate), including erythema, itching and burning, are the most commonly reported adverse events, occurring in < or = 67% of patients applying imiquimod 5% cream 3 times a week. The incidence of adverse events is lower in patients applying the cream 3 times a week than with daily application. The incidence of systemic adverse events with imiquimod 5% cream (applied daily or 3 times a week) is similar to that of vehicle cream. The tolerability profile of imiquimod cream appears favourable compared with that of podophyllotoxin.

CONCLUSION

Imiquimod 5% cream is a new therapeutic option for patients with genital warts. It produces clearance rates broadly similar to those of other treatment approaches and rates of wart recurrence compare favourably with those reported for established treatments. In contrast to most alternative treatment strategies. which are administered in the physician's office, imiquimod cream is a self-administered therapy for outpatient use.

Application of the differential display RT-PCR strategy for the identification of inflammation-related mouse genes

The inflammatory response elicited by various stimuli such as microbial products or cytokines is determined by differences in the pattern of cellular gene expression. We have used the differential display RT-PCR (DDRT-PCR) strategy to identify mRNAs that are differentially expressed in various murine cell types stimulated with pro-inflammatory cytokines, microbial products or anti-inflammatory drugs. Mouse embryonic fibroblasts (MEFs) were treated with IFNs, TNF, or sodium salicylate. Also, peritoneal macrophages from C3H/Hej mice were stimulated with T. cruzi-derived GPI-mucin and/or IFN-gamma. After DDRT-PCR, various cDNA fragments that were differentially represented on the sequencing gel were recovered, cloned and sequenced. Here, we describe a summary of several experiments and show that, when 16 of a total of 28 recovered fragments were tested for differential expression, 5 (31%) were found to represent mRNAs whose steady-state levels are indeed modulated by the original stimuli. Some of the identified cDNAs encode for known proteins that were not previously associated with the inflammatory process triggered by the original stimuli. Other cDNA fragments (8 of 21 sequences, or 38%) showed no significant homology with known sequences and represent new mouse genes whose characterization might contribute to our understanding of inflammation. In conclusion, DDRT-PCR has proven to be a potent technology that will allow us to identify genes that are differentially expressed when cells are subjected to changes in culture conditions or isolated from different organs.

The immune response modifier imiquimod requires STAT-1 for induction of interferon, interferon-stimulated genes, and interleukin-6

Imiquimod is an oral inducer of interferon (IFN) and several other proinflammatory cytokines and has been successfully used topically as an antiviral agent for the treatment of genital warts. We have investigated the molecular mechanisms by which imiquimod induces the expression of IFNs, IFN-stimulated genes (ISGs), and proinflammatory cytokines in vivo, using mice deficient in various components of the IFN signaling system. Mice deficient in the transcription factor interferon regulatory factor 1 (IRF-1) or in the serine/threonine protein kinase PKR responded normally to imiquimod, producing high levels of circulating IFN and induction of several ISGs. On the other hand, when mice deficient in STAT-1 were treated, a 32-fold reduction in the level of circulating IFN was observed, together with a lack of induction of 2-5 oligo adenylate synthetase (2-5 OAS) and IRF-1 genes. Interestingly, there was also a lack of induction of interleukin-6 (IL-6) gene expression, although tumor necrosis factor was induced and readily detected in serum. In mice deficient in the type I IFN receptor, imiquimod induced levels of IFN similar to those in control mice, but again, neither 2-5 OAS, IRF-1, nor IL-6 genes were induced in mutant mice. Our results suggest that STAT-1 plays a critical role in the mechanism of gene activation by imiquimod. Moreover, induction of IL-6 gene expression appears to be dependent on components of the IFN signaling cascade.

Imiquimod applied topically: a novel immune response modifier and new class of drug

Imiquimod (S-26308, R-837) (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4 amine), an immune response modifier, demonstrates potent antiviral and antitumor activity in animal models (see structure in Fig. 1). The drug exhibits no direct antiviral or antiproliferative activity when tested in a number of cell culture systems. Imiquimod's activity was discovered while screening for anti-herpes virus activity. One of the first analogs in the series, S-25059 was tested in the early 1980's and due to slight toxicity, caused slightly reduced herpes cytopathology in Vero cell cultures. Follow-up testing in herpes infected guinea pigs showed complete protection toward lesion development. Activity of these drugs results primarily from interferon alpha (IFN-alpha) induction and other cytokine induction. At least part of the cytokine induction is mediated through NF-kappaB activation. These cytokines stimulate several other aspects of the innate immune response. In addition, imiquimod stimulates acquired immunity, in particular the cellular arm which is important for control of viral infections and various tumors. This effect is mediated by drug induced IFN-alpha and Interleukin-12 (IL-12) and IFN-gamma induced by these cytokines. Imiquimod is expected to be effective where exogenous IFN-alpha has shown utility and where enhancement of cell-mediated immunity is needed. The following is a brief review of the preclinical pharmacology of imiquimod and the clinical results of genital wart trials. The mechanism of action of topically applied imiquimod will likely lead to benefits in several other chronic virus infections and tumors of the skin. Two other reviews on imiquimod that focus mainly on the clinical results have been published (Beutner & Geisse, 1997; Slade, Owens, Tomai & Miller, 1998).

Antiviral treatment of diseases in pediatric dermatology

Pediatric dermatologic disease that have specific therapies and/or specific prophylactic measures are reviewed. Herpes simplex virus and varicella-zoster virus infections, human papillomavirus infections, and molluscum contagiosum infections are discussed with special emphasis on recent advances of therapy and prophylaxis.