Mark E. Polhemus

Evaluation of RTS,S/AS02A and RTS,S/AS01B in Adults in a High Malaria Transmission Area

Background This study advances the clinical development of the RTS,S/AS01B candidate malaria vaccine to malaria endemic populations. As a primary objective it compares the safety and reactogenicity of RTS,S/AS01B to the more extensively evaluated RTS,S/AS02A vaccine. Methodology A Phase IIb, single centre, double-blind, controlled trial of 6 months duration with a subsequent 6 month single-blind follow-up conducted in Kisumu West District, Kenya between August 2005 and August 2006. 255 healthy adults aged 18 to 35 years were randomized (1∶1∶1) to receive 3 doses of RTS,S/AS02A, RTS,S/AS01B or rabies vaccine (Rabipur®; Chiron Behring GmbH) at months 0, 1, 2. The primary objective was the occurrence of severe (grade 3) solicited or unsolicited general (i.e. systemic) adverse events (AEs) during 7 days follow up after each vaccination. Principal Findings Both candidate vaccines had a good safety profile and were well tolerated. One grade 3 systemic AE occurred within 7 days of vaccination (RTS,S/AS01B group). No unsolicited AEs or SAEs were related to vaccine. A marked increase in anti-CS antibody GMTs was observed post Dose 2 of both RTS,S/AS01B (31.6 EU/mL [95% CI: 23.9 to 41.6]) and RTS,S/AS02A (16.7 EU/mL [95% CI: 12.9 to 21.7]). A further increase was observed post Dose 3 in both the RTS,S/AS01B (41.4 EU/mL [95% CI: 31.7 to 54.2]) and RTS,S/AS02A (21.4 EU/mL [95% CI: 16.0 to 28.7]) groups. Anti-CS antibody GMTs were significantly greater with RTS,S/AS01B compared to RTS,S/AS02A at all time points post Dose 2 and Dose 3. Both candidate vaccines produced strong anti-HBs responses. Vaccine efficacy in the RTS,S/AS01B group was 29.5% (95% CI: −15.4 to 56.9, p = 0.164) and in the RTS,S/AS02A group 31.7% (95% CI: −11.6 to 58.2, p = 0.128). Conclusions Both candidate malaria vaccines were well tolerated over a 12 month surveillance period. A more favorable immunogenicity profile was observed with RTS,S/AS01B than with RTS,S/AS02A. Trial Registration Clinicaltrials.gov NCT00197054

Antimalarial Drug Sensitivity Profile of Western Kenya Plasmodium falciparum Field Isolates Determined by a SYBR Green I in vitro Assay and Molecular Analysis

In vitro drug sensitivity and molecular analyses of Plasmodium falciparum track drug resistance. DNA-binding fluorescent dyes like SYBR Green I may allow field laboratories, proximal to P. falciparum collection sites, to conduct drug assays. In 2007-2008, we assayed 121 P. falciparum field isolates from western Kenya for 50% inhibitory concentrations (IC(50)) against 6 antimalarial drugs using a SYBR Green I in vitro assay: 91 immediate ex vivo (IEV) and 30 culture-adapted, along with P. falciparum reference clones D6 (chloroquine [CQ] sensitive) and W2 (CQ resistant). We also assessed P. falciparum mdr1 (Pfmdr1) copy number and single nucleotide polymorphisms (SNPs) at four codons. The IC(50)s for IEV and culture-adapted P. falciparum isolates were similar, and approximated historical IC(50)s. For Pfmdr1, mean copy number was 1, with SNPs common at codons 86 and 184. The SYBR Green I assay adapted well to our field-based laboratory, for both IEV and culture-adapted P. falciparum, warranting continued use.

Outpatient Upper Respiratory Tract Viral Infections in Children with Malaria Symptoms in Western Kenya

A cross-sectional study was performed in children 5 through 10 years of age presenting to outpatient clinics in Nyanza Province, Kenya, in which nasal swab and blood specimens were collected during the high malaria transmission season. Patients presenting with malaria-like symptoms within 4 days of fever onset were enrolled in the study. Plasmodium parasitemia was determined by blood smear microscopy. Nasal swabs were screened for a panel of respiratory viruses by polymerase chain reaction. Influenza A, rhinoviruses, and other respiratory viruses were detected in 18%, 26%, and 12% of 197 specimens, respectively. Four of 36 patients with influenza A had a positive malaria blood slide, compared with 20 of 52 patients with rhinovirus. A significant burden of disease caused by influenza A in febrile children during the study period was observed, highlighting the need for further research into the burden of influenza disease in regions where malaria is holoendemic.

Evaluation of recurrent parasitemia after artemether-lumefantrine treatment for uncomplicated malaria in children in western Kenya.

From April 2005 to April 2006, a phase 2 malaria vaccine trial in Kenya enrolled 400 children aged 12-47 months. Each received mixed supervised and unsupervised artemether-lumefantrine for uncomplicated malaria, using a standard six-dose regimen, by weight. Children were followed for detection of parasitemia and clinical malaria. A median of two negative malaria blood films occurred during every recurrent parasitemia (RP) episode, suggesting reinfection over late recrudescence. Median time to RP after starting artemether-lumefantrine was 37 days (36-38). Of 2,020 evaluable artemether-lumefantrine treatments, there were no RPs in 99% by day 14, 71% by day 28, and 41% by day 42. By World Health Organization standards, 71% of treatment courses had adequate responses. Although recrudescence in some cannot be ruled out, our cohort had a shorter median time to RP compared with other artemether-lumefantrine treatment studies. This underscores patient counseling on completing all treatment doses for optimal protection from RP.

Bullous erythema multiforme after treatment with Malarone®, a combination antimalarial composed of atovaquone and proguanil hydrochloride

We report on a Kenyan woman who developed bullous erythema multiforme, in association with Malarone treatment.

Malaria Treatment with Atovaquone-Proguanil in Malaria-Immune Adults: Implications for Malaria Intervention Trials and for Pre-Exposure Prophylaxis of Malaria

ABSTRACT Eighty adults in areas of Kenya where malaria is holoendemic received presumptive treatment with atovaquone-proguanil and were followed closely. The time to the first Plasmodium falciparum parasitemia was 32 days. This prolonged prophylaxis period has implications for study design when used in malaria intervention trials and cautiously suggests clinical investigation of potential preexposure prophylaxis of malaria.

Adenovirus type 35-vectored tuberculosis vaccine has an acceptable safety and tolerability profile in healthy, BCG-vaccinated, QuantiFERON(®)-TB Gold (+) Kenyan adults without evidence of tuberculosis.

In a Phase 1 trial, we evaluated the safety of AERAS-402, an adenovirus 35-vectored TB vaccine candidate expressing 3 Mycobacterium tuberculosis (Mtb) immunodominant antigens, in subjects with and without latent Mtb infection. HIV-negative, BCG-vaccinated Kenyan adults without evidence of tuberculosis, 10 QuantiFERON(®)-TB Gold In-Tube test (QFT-G)(-) and 10 QFT-G(+), were randomized 4:1 to receive AERAS-402 or placebo as two doses, on Days 0 and 56, with follow up to Day 182. There were no deaths, serious adverse events or withdrawals. For 1 AERAS-402 QFT-G(-) and 1 AERAS-402 QFT-G(+) subject, there were 3 self-limiting severe AEs of injection site pain: 1 after the first vaccination and 1 after each vaccination, respectively. Two additional severe AEs considered vaccine-related were reported after the first vaccination in AERAS-402 QFT-G(+) subjects: elevated blood creatine phosphokinase and neutropenia, the latter slowly improving but remaining abnormal until study end. AERAS-402 was not detected in urine or throat cultures for any subject. In intracellular cytokine staining studies, curtailed by technical issues, we saw modest CD4+ and CD8+ T cell responses to Mtb Ag85A/b peptide pools among both QFT-G(-) and (+) subjects, with trends in the CD4+ T cells suggestive of boosting after the second vaccine dose, slightly more so in QFT-G(+) subjects. CD4+ and CD8+ responses to Mtb antigen TB10.4 were minimal. Increases in Adenovirus 35 neutralizing antibodies from screening to end of study, seen in 50% of AERAS-402 recipients, were mostly minimal. This small study confirms acceptable safety and tolerability profiles for AERAS-402, in line with other Phase 1 studies of AERAS-402, now to include QFT-G(+) subjects.

Pharmacokinetic evaluation of intravenous artesunate in adults with uncomplicated falciparum malaria in Kenya: a phase II study

BackgroundAlternatives to treatment for malaria treatment of travellers are needed in the USA and in Europe for travellers who return with severe malaria infections. The objective of this study is to show the pharmacokinetic (PK) profile of intravenous artesunate (AS), which was manufactured under good manufacturing practice (GMP) conditions, in adults with uncomplicated falciparum malaria in Kenya.MethodsThe PK parameters of intravenous AS manufactured under current cGMP were evaluated after a single dose of drug at 2.4 mg/kg infused over 2 min in 28 adults with uncomplicated Plasmodium falciparum malaria. Plasma concentrations of AS and dihydroartemisinin (DHA) were measured using a validated liquid chromatography–mass spectrometry (LC-MS/MS) methodology. Pharmacokinetic data were analysed with a compartmental analysis for AS and DHA.ResultsThe results suggest there were no drug-related adverse events in any of the patients. After intravenous infusion, the concentration of the parent drug rapidly declined, and the AS was converted to DHA. AS and DHA showed mean elimination half-lives of 0.17 hours and 1.30 hours, respectively. The high mean peak concentration (Cmax) of AS was shown to be 28,558 ng/mL while the Cmax of DHA was determined to be 2,932 ng/mL. Significant variability was noted in the PK profiles of the 28 patients tested. For example, Cmax values of AS were calculated to range from 3,362 to 55,873 ng/mL, and the Cmax value of DHA was noted to vary from 1,493 to 5,569 ng/mL. The mean area under the curve (AUC) of AS was shown to be approximately half that of DHA (1,878 ng·h/mL vs 3,543 ng·h/mL). The DHA/AS ratio observed was 1.94 during the one-day single treatment, and the AUC and half- life measured for DHA were significantly larger and longer than for AS.ConclusionsIntravenous AS can provide much higher peak concentrations of AS when compared to concentrations achieved with oral therapy; this may be crucial for the rapid elimination of parasites in patients with severe malaria. Given the much longer half-life of DHA compared to the short half-life of AS, DHA also plays a significant role in treatment of severe malaria.

Phase 2a, Open-Label, 4-Escalating-Dose, Randomized Multicenter Study Evaluating the Safety and Activity of Ferroquine (SSR97193) Plus Artesunate, versus Amodiaquine Plus Artesunate, in African Adult Men with Uncomplicated Plasmodium falciparum Malaria.

Artemisinin-based combination therapies are recommended as first-line agents for treating uncomplicated Plasmodium falciparum malaria. Ferroquine, a 4-aminoquinolone, is a novel long-acting combination partner for fast-acting drugs like artesunate (AS). We did a small phase 2a, multicenter, open-label, safety-focused dose-ranging randomized study of ferroquine at three African hospitals: two Gabonese and one Kenyan. We recruited adult men with symptomatic uncomplicated P. falciparum monoinfection. Four escalating doses of ferroquine (100, 200, 400, and 600 mg) were assessed in sequence, versus an amodiaquine comparator. After a 2:1 randomization (block size three, equating to N = 12 for each ferroquine dose and N = 6 for each of four amodiaquine comparator groups) patients received daily for three consecutive days, either ferroquine + AS (200 mg/day) or amodiaquine (612 mg/day) + AS (200 mg/day). Safety, electrocardiograms, parasite clearance times, efficacy, and pharmacokinetics were assessed to day 28. Seventy-two patients were randomized. Ferroquine + AS showed generally mild increases (Grade 1 toxicity) in alanine aminotransferase (ALT) levels with a dose trend starting at 400 mg. There were two Grade 2 ALT events: one patient receiving 200 mg (3.8 upper limit of normal [ULN], day 7) and one receiving 600 mg (3.3 ULN, day 14), both without increased bilirubin. One ferroquine 100 mg + AS patient after one dose was withdrawn after developing a QTcF interval prolongation > 60 milliseconds over baseline. Parasitemias in all patients cleared quickly, with no recurrence through day 28. Hepatic, as well as cardiac, profiles should be monitored closely in future trials. (ClinicalTrials.gov: NCT00563914).

Persistence of Vaccinia at the Site of Smallpox Vaccination

Persistence of vaccinia at vaccination sites may help determine the risk associated with secondary transmission. Culture, PCR, and antigen detection were performed on serial vaccination site swab specimens. On day 21 after vaccination, 37% of volunteers were culture positive, most of whom had received vaccine for the first time. Vaccinia is detectable at least through day 21 after vaccination.