Tafenoquine exposure assessment, safety, and relapse prevention efficacy in children with Plasmodium vivax malaria: open-label, single-arm, non-comparative, multicentre, pharmacokinetic bridging, phase 2 trial.

BACKGROUND: Single-dose tafenoquine 300 mg is approved for Plasmodium vivax malaria relapse prevention in patients at least 16 years old. We aimed to determine appropriate oral tafenoquine paediatric dosing regimens, including a dispersible formulation, and evaluated tafenoquine efficacy and safety in children infected with P vivax. METHODS: This open-label, single-arm, non-comparative, multicentre, pharmacokinetic bridging, phase 2 study enrolled children (2-15 years) who weighed 5 kg or more, with glucose-6-phosphate dehydrogenase activity more than 70% of the local population median, and P vivax malaria infection, from three community health centres in Vietnam and one in Colombia. Patients received 3-day chloroquine plus oral single-dose tafenoquine as dispersible tablets (50 mg) or film-coated tablets (150 mg). Dosing groups were assigned by body weight, predicted to achieve similar median exposures as the approved 300 mg dose for adults: patients who weighed 5 kg or more to 10 kg received 50 mg, those who weighed more than 10 to 20 kg received 100 or 150 mg, those who weighed more than 20 to 35 kg received 200 mg, and patients who weighed more than 35 kg received 300 mg. Population pharmacokinetic analysis was done to develop a paediatric population pharmacokinetic model. The primary outcome was the tafenoquine area under the concentration-time curve extrapolated to infinity (AUC[0-∞]) by patient body weight in the pharmacokinetic population (all patients who received tafenoquine with at least one valid pharmacokinetic sample) estimated from a paediatric population pharmacokinetic model. A key prespecified secondary outcome was 4-month recurrence-free efficacy. This trial is registered with ClinicalTrials.gov, NCT02563496. FINDINGS: Between Feb 6, 2017, and Feb 17, 2020, 60 patients were enrolled into the study: 14 (23%) received tafenoquine 100 mg, five (8%) 150 mg, 22 (36%) 200 mg, and 19 (32%) 300 mg. The paediatric population pharmacokinetic model predicted adequate tafenoquine exposure at all doses. The predicted median AUC(0-∞) was 73·8 (90% prediction interval [PI] 46·9-117·0) µg × h/mL with the 50 mg dose for patients who weighed 5 kg or more to 10 kg, 87·5 (55·4-139·0) µg × h/mL with the 100 mg dose for body weight more than 10 to 20 kg, 110·7 (70·9-174·0) µg × h/mL with the 200 mg dose for body weight more than 20 to 35 kg, and 85·7 (50·6-151·0) µg × h/mL with the 300 mg dose for body weight more than 35 kg. 4-month recurrence-free efficacy was 94·7% (95% CI 84·6-98·3). Adverse events were consistent with previous studies, except for the seven (12%) of 60 patients who had post-dose vomiting or spitting with the 50 mg dispersed tablet. Following mitigation strategies, there were no additional occurrences of this adverse event. There were no deaths during the study. INTERPRETATION: For the prevention of P vivax relapse in children, single-dose tafenoquine, including a dispersible formulation, had exposure, safety, and efficacy consistent with observations in adolescents and adults, notwithstanding post-dose vomiting. FUNDING: GlaxoSmithKline and Medicines for Malaria Venture. TRANSLATIONS: For the Vietnamese and Spanish translations of the abstract see Supplementary Materials section.

Pharmacogenetic assessment of tafenoquine efficacy in patients with Plasmodium vivax malaria.

Plasmodium vivax has the largest geographic range of human malaria species and is challenging to manage and eradicate due to its ability to establish a dormant liver stage, the hypnozoite, which can reactivate leading to relapse. Until recently, the only treatment approved to kill hypnozoites was the 8-aminoquinoline, primaquine, requiring daily treatment for 14 days. Tafenoquine, an 8-aminoquinoline single-dose treatment with activity against P. vivax hypnozoites, has recently been approved by the US Food and Drug Administration and Australian Therapeutic Goods Administration for the radical cure of P. vivax malaria in patients 16 years and older. We conducted an exploratory pharmacogenetic analysis (GSK Study 208099) to assess the role of host genome-wide variation on tafenoquine efficacy in patients with P. vivax malaria using data from three GSK clinical trials, GATHER and DETECTIVE Part 1 and Part 2. Recurrence-free efficacy at 6 and 4 months and time to recurrence up to 6 months postdosing were analyzed in 438 P. vivax malaria patients treated with tafenoquine. Among the approximately 10.6 million host genetic variants analyzed, two signals reached genome-wide significance (P value ≤ 5 × 10). rs62103056, and variants in a chromosome 12 intergenic region, were associated with recurrence-free efficacy at 6 and 4 months, respectively. Neither of the signals has an obvious biological rationale and would need replication in an independent population. This is the first genome-wide association study to evaluate genetic influence on response to tafenoquine in P. vivax malaria.

Cost-Effectiveness Analysis of Sex-Stratified Plasmodium vivax Treatment Strategies Using Available G6PD Diagnostics to Accelerate Access to Radical Cure.

Tafenoquine has been licensed for the single-dose radical cure of Plasmodium vivax in adults; however, it is only recommended in patients with > 70% of normal glucose-6-phosphate dehydrogenase (G6PD) activity. Because this may hinder widespread use, we investigated sex-based treatment strategies in which all adult patients are tested with a qualitative G6PD rapid diagnostic test (RDT). Glucose-6-phosphate dehydrogenase normal males are prescribed tafenoquine in all three strategies, whereas G6PD normal females are prescribed either a low-dose 14-day primaquine regimen (PQ14, total dose 3.5 mg/kg) or a high-dose 7-day primaquine regimen (PQ7, total dose 7 mg/kg), or referred to a healthcare facility for quantitative G6PD testing before prescribing tafenoquine. Patients testing G6PD deficient are prescribed a weekly course of primaquine for 8 weeks. We compared the cost-effectiveness of these three strategies to usual care in four countries using a decision tree model. Usual care in Ethiopia does not include radical cure, whereas Afghanistan, Indonesia, and Vietnam prescribe PQ14 without G6PD screening. The cost per disability-adjusted life-year (DALY) averted was expressed through incremental cost-effectiveness ratios (ICERs). Compared with usual care, the ICERs for a sex-based treatment strategy with PQ7 for females from a healthcare provider perspective were $127 per DALY averted in Vietnam, $466 in Ethiopia, $1,089 in Afghanistan, and $4,443 in Indonesia. The PQ14 and referral options cost more while averting fewer DALYs than PQ7. This study provides an alternative cost-effective mode of rolling out tafenoquine in areas where initial testing with only a G6PD RDT is feasible.

Comparative ophthalmic assessment of patients receiving tafenoquine or chloroquine/primaquine in a randomized clinical trial for Plasmodium vivax malaria radical cure.

PURPOSE: Ophthalmic safety observations are reported from a clinical trial comparing tafenoquine (TQ) efficacy and safety versus sequential chloroquine (CQ)/primaquine (PQ) for acute Plasmodium vivax malaria. METHODS: In an active-control, double-blind study, 70 adult subjects with microscopically confirmed P. vivax malaria were randomized (2:1) to receive 400 mg TQ × 3 days or 1500 mg CQ × 3 days then 15 mg PQ × 14 days. MAIN OUTCOME MEASURES: clinically relevant changes at Day 28 and Day 90 versus baseline in the ocular examination, color vision evaluation, and corneal and retinal digital photography. RESULTS: Post-baseline keratopathy occurred in 14/44 (31.8%) patients with TQ and 0/24 with CQ/PQ (P = 0.002). Mild post-baseline retinal findings were reported in 10/44 (22.7%) patients receiving TQ and 2/24 (8.3%) receiving CQ/PQ (P = 0.15; treatment difference 14.4%, 95% CI - 5.7, 30.8). Masked evaluation of retinal photographs identified a retinal hemorrhage in one TQ patient (Day 90) and a slight increase in atrophy from baseline in one TQ and one CQ/PQ patient. Visual field sensitivity (Humphrey™ 10-2 test) was decreased in 7/44 (15.9%) patients receiving TQ and 3/24 (12.5%) receiving CQ/PQ; all cases were < 5 dB. There were no clinically relevant changes in visual acuity or macular function tests. CONCLUSIONS: There was no evidence of clinically relevant ocular toxicity with either treatment. Mild keratopathy was observed with TQ, without conclusive evidence of early retinal changes. Eye safety monitoring continues in therapeutic studies of low-dose tafenoquine (300 mg single dose). CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT01290601.

Cost-efficacy analysis of 3% diclofenac sodium, ingenol mebutate, and 3.75% imiquimod in the treatment of actinic keratosis.

Actinic keratosis (AK) is a clinical condition characterized by keratinocytic dysplastic lesions of the epidermis, affecting individuals chronically exposed to sunlight. Topical therapies allow the treatment of a whole area of affected skin and currently include diclofenac sodium gel, 5-fluorouracil cream, 5-fluorouracil and acetylsalicylic acid solution, imiquimod cream, and ingenol mebutate gel. Due to the comparable efficacy of 3% diclofenac, ingenol mebutate, and 3.75% imiquimod in treating AK multiple lesions, a pharmacoeconomic evaluation of cost-effectiveness of the three treatments was needed. A cost-efficacy analysis comparing 3% diclofenac sodium with ingenol mebutate and 3.75% imiquimod was performed. In this analysis, efficacy data were combined with quality-of-life measurement derived from previous studies as well as the costs associated with the management of these lesions in Italy. Patients' demographics and clinical characteristics were assumed to reflect those from the clinical studies considered.

Cost-Effectiveness and Cost-Utility Analysis of Ingenol Mebutate Versus Diclofenac 3% and Imiquimod 5% in the Treatment of Actinic Keratosis in Spain. / Análisis de coste-efectividad y coste-utilidad de ingenol mebutato versus diclofenaco 3% e imiquimod 5% en el tratamiento de la queratosis actínica en España.

OBJECTIVE: To perform a cost-effectiveness and cost-utility analysis of ingenol mebutate in the treatment of actinic keratosis in Spain. METHODS: We used an adapted Markov model to simulate outcomes in a cohort of patients (mean age, 73 years) with actinic keratosis over a 5-year period. The comparators were diclofenac 3% and imiquimod 5%. The analysis was performed from the perspective of the Spanish National Health System based on direct costs (2015 retail price plus value added tax less the mandatory discount). A panel of experts estimated resources, taking unit costs from national databases. An annual discount rate of 3% was applied. Deterministic and probabilistic sensitivity analyses were performed. RESULTS: The effectiveness of ingenol mebutate-with 0.192 and 0.129 more clearances gained in treatments for face and scalp lesions and trunk and extremity lesions, respectively-was superior to diclofenac's. The total costs of treatment with ingenol mebutate were lower at € 551.50 (face and scalp) and € 622.27 (trunk and extremities) than the respective costs with diclofenac (€ 849.11 and € 844.93). The incremental cost-effectiveness and cost-utility ratios showed that ingenol mebutate was a dominant strategy vs diclofenac. Ingenol mebutate also proved to be more effective than imiquimod, based on 0.535 and 0.503 additional clearances, and total costs of € 551.50 and € 527.89 for the two drugs, respectively. The resulting incremental cost-effectiveness ratio was € 728.64 per clearance gained with ingenol mebutate vs imiquimod. CONCLUSIONS: Ingenol mebutate was a dominant treatment option vs diclofenac and was efficient vs imiquimod (i.e., more effective at a higher cost, achieving an incremental cost-utility ratio of<€30000/quality-adjusted life-years).

Cost-effectiveness of topical imiquimod and fluorouracil vs. photodynamic therapy for treatment of superficial basal-cell carcinoma.

BACKGROUND: A recent noninferiority randomized trial showed that in terms of clinical effectiveness imiquimod was superior and topical fluorouracil noninferior to methylaminolaevulinate photodynamic therapy (MAL-PDT) for treatment of superficial basal-cell carcinoma (sBCC). Although it was expected that MAL-PDT would be more costly than either cream, a full cost-effectiveness analysis is necessary to determine the balance between effectiveness and costs. OBJECTIVE: To determine whether imiquimod or topical fluorouracil are cost-effective treatments for sBCC compared with MAL-PDT. METHODS: An economic evaluation was performed from a healthcare perspective. Data on resource use and costs were collected alongside the randomized clinical trial. The incremental cost-effectiveness ratio was expressed as the incremental costs per additional patient free of tumour recurrence. RESULTS: At 12 months follow-up, the total mean costs for MAL-PDT were €680, for imiquimod cream €526 and for topical fluorouracil cream €388. Both imiquimod and topical fluorouracil were cost-effective treatments compared with MAL-PDT. Comparing costs and effectiveness of both creams led to a incremental investment of €4451 to achieve an additional patient free of tumour recurrence. The acceptability curve showed that, for a threshold value of €4451, the probability of imiquimod being more cost-effective than topical fluorouracil was 50%. CONCLUSION: Based on the 12 months follow-up results, imiquimod and topical fluorouracil cream are more cost-effective than MAL-PDT for treatment of sBCC. Hence, substituting MAL-PDT with either imiquimod or topical fluorouracil results in cost savings; these savings will be larger for topical fluorouracil. Long-term follow-up effectiveness data are necessary to confirm the cost-effectiveness of imiquimod vs. topical 5-fluorouracil cream.

Topical and intralesional treatment of nonmelanoma skin cancer: efficacy and cost comparisons.

BACKGROUND: Topical chemotherapy, topical immunomodulators, or intralesional chemotherapy may be used to treat nonmelanoma skin cancer (NMSC). OBJECTIVES: To review the cost and efficacy of topical and intralesional therapies for NMSC. METHODS: Literature search assessing the efficacy of NMSC treatment with topical imiquimod, topical 5-fluorouracil (5FU) intralesional 5FU, methotrexate, bleomycin, and interferon (IFN). Single-lesion case reports were excluded. Aggregate cure rates and the estimated cost of treatment (including excision and repair of recurrent lesions) for a sample 1-cm lesion on an extremity were calculated. RESULTS: Cure rates ranged from 65% to 100% for topical imiquimod and 61% to 92% for 5FU. For intralesional agents, cure rates varied considerably according to medication used and NMSC subtype treated. Keratoacanthomas had high cure rates with intralesional agents: 98% for 5FU, 91% for methotrexate, 100% for bleomycin, 100% for IFN alpha (α)-2, 83% for IFN α-2a, and 100% for IFN α-2b. Estimated costs (excluding medication cost) ranged from $205 (intralesional methotrexate for keratoacanthoma) to $1,174 (IFN α-2a for superficial basal cell carcinoma). CONCLUSION: Nonsurgical management of NMSC remains a viable and relatively cost effective treatment option in select cases. Providers should consider the relative efficacy and cost of each medication when using nonsurgical modalities.

What determines patient preferences for treating low risk basal cell carcinoma when comparing surgery vs imiquimod? A discrete choice experiment survey from the SINS trial.

BACKGROUND: The SINS trial (Controlled Clinical Trials ISRCTN48755084; Eudract No. 2004-004506-24) is a randomised controlled trial evaluating long term success of excisional surgery vs. imiquimod 5% cream for low risk nodular and superficial basal cell carcinoma (BCC). The trial included a discrete choice experiment questionnaire to explore patient preferences of a cream versus surgery for the treatment of their skin cancer. METHODS: The self-completed questionnaire was administered at baseline to 183 participants, measuring patients' strength of preferences when choosing either alternative 'surgery' or 'imiquimod cream' instead of a fixed 'current situation' option (of surgical excision as standard practice in UK). The treatments were described according to: cost, chance of complete clearance, side effects and appearance. Participants had to choose between various scenarios. Analysis was performed using a mixed logit model, which took into account the impact of previous BCC treatment and sample preference variability. RESULTS: The analysis showed that respondents preferred 'imiquimod cream' to their 'current situation' or 'surgery', regardless of previous experience of BCC symptoms and treatment. Respondents were more likely to be worried about their cosmetic outcomes and side effects they might experience over and above their chance of clearance and cost. Those with no experience of surgery (compared with experience) valued more the choice of 'imiquimod cream' (£1013 vs £781). All treatment characteristics were significant determinants of treatment choice, and there was significant variability in the population preferences for all of them. CONCLUSIONS: Patients with BCC valued more 'imiquimod cream' than alternative 'surgery' options, and all treatment characteristics were important for their choice of care. Understanding how people with a BCC value alternative interventions may better inform the development of health care interventions.

Cost effectiveness of imiquimod 5% cream compared with methyl aminolevulinate-based photodynamic therapy in the treatment of non-hyperkeratotic, non-hypertrophic actinic (solar) keratoses: a decision tree model.

BACKGROUND: Actinic keratosis (AK) is caused by chronic exposure to UV radiation (sunlight). First-line treatments are cryosurgery, topical 5-fluorouracil (5-FU) and topical diclofenac. Where these are contraindicated or less appropriate, alternatives are imiquimod and photodynamic therapy (PDT). OBJECTIVE: To compare the cost effectiveness of imiquimod and methyl aminolevulinate-based PDT (MAL-PDT) from the perspective of the UK NHS. METHODS: A decision tree model was populated with data from a literature review and used to estimate costs and QALYs gained and incremental cost effectiveness over 1 year. The model simulated patients who were in secondary care, who had four to nine AK lesions, and for whom cryosurgery, 5-FU and diclofenac were contraindicated or considered less appropriate. RESULTS: Over 1 year, imiquimod cost £174 less than MAL-PDT (year 2006 values) but resulted in 0.005 fewer QALYs gained. The incremental cost-effectiveness ratio (ICER) of MAL-PDT over imiquimod was £34,576. In the probabilistic sensitivity analysis, there was a 75% probability that imiquimod was cost effective compared with MAL-PDT at a threshold of £20,000 per QALY gained, falling to 73% at £30,000. CONCLUSIONS: Imiquimod may be the more cost-effective treatment at conventional cost-effectiveness thresholds. A direct head-to-head study of MAL-PDT versus imiquimod is required to reduce uncertainty.

The SINS trial: a randomised controlled trial of excisional surgery versus imiquimod 5% cream for nodular and superficial basal cell carcinoma.

BACKGROUND: Basal cell carcinoma is the commonest human cancer. Despite increasing incidence it remains poorly researched. While not life threatening it can cause significant cosmetic disfigurement. Imiquimod, a cream which enhances the body's immune response, may help deal with the number of cases that occur in low-risk sites, especially when good cosmetic results and home use without surgery are needed.This study aims 1. To compare excisional surgery with imiquimod cream for nodular or superficial basal cell carcinoma in low risk sites, with respect to 3 year clinical clearance, cost-effectiveness and cosmetic results. 2. To ascertain if certain phenotypic features and gene polymorphisms predict tumour responsiveness to treatment. METHODS/DESIGN: Five hundred participants with low risk nodular or superficial basal cell carcinoma will be recruited from hospitals to this multi-centre, randomised, parallel group, controlled phase III trial. Treatment in the imiquimod group is for 6 weeks for superficial basal cell carcinoma and 12 weeks for nodular basal cell carcinoma. Both treatment groups are followed up in clinic for 3 years. Primary outcome variable: the proportion of participants with clinical evidence of success (no recurrence) at 3 years. The primary outcome will be compared between the two treatment groups. Secondary outcomes include: i) clinical success at 1, 2 and 5 years, ii) time to first recurrence, iii) cosmetic appearance of lesion site after treatment, iv) level of pain, and v) cost-effectiveness. Safety and tolerability data will also be reported. DISCUSSION: This study protocol describes a pragmatic randomised controlled trial which it is hoped will address the above uncertainties. Three-year results will be available towards the end of 2010. TRIAL REGISTRATION: Meta-register: NCT00066872, Eudract No. 2004-004506-24, ISRCTN48755084.

Imiquimod and superficial skin cancers.

Topical imiquimod has opened an entirely new area of dermatology that previously did not exist: medical therapy for skin cancers. While surgery will continue to play a vital role in treating more aggressive tumors and in patients who may not be imiquimod candidates, the availability of a viable medical therapy that can be used independently or in combination with other modalities will considerably enhance our ability to treat skin cancer successfully.

The cost effectiveness of patient-applied versus provider-administered intervention strategies for the treatment of external genital warts.

OBJECTIVE: External genital warts are one of the fastest growing sexually transmitted diseases in the United States today. Two forms of therapy are available: provider-administered and patient-applied. In the most widely used provider-administered ablative therapies, sustained clearance rates range from 18.5% to 40.1%. With nonablative, patient-applied therapies, which are typically more acceptable to patients, sustained clearance rates range from 19.6% with podofilox gel to 44.0% with imiquimod cream. The purpose of this study, given the range of therapies available, their cost differences, and clinical trial-reported differences in rates of sustained clearance, is to determine which therapy modalities, from the providers' perspective, are the most cost effective and which are likely to be the most acceptable to the patient population. STUDY DESIGN: We consider the cost effectiveness of the two patient-applied therapies as first-line therapy followed by provider-administered ablative treatment as second-line therapy. A decision-analytic model framework is developed, with data drawn both from clinical trials and from previously published studies. RESULTS: When considering a two-stage therapy model, with an average sustained clearance rate of 30% assumed for provider-administered ablative therapies, estimated costs per sustained cleared patient are $1265 for patients initially treated with imiquimod and $1304 for patients initially treated with podofilox gel. CONCLUSIONS: Initial treatment with imiquimod is the preferred intervention option as it yields a 39% greater sustained clearance rate than podofilox gel while being 3% less costly per successful outcome.