BENDITA BEnznidazole New Doses Improved Treatment and Associations

The current treatment for Chagas disease has significant limitations, including long treatment durations, safety and tolerability concerns and is currently limited to two nitro-heterocyclic drugs, nifurtimox and benznidazole (BZN). BZN, a nitroimidazole introduced by Roche in 1971, is marketed by Laboratório Farmacêutico do Estado de Pernambuco S/A - LAFEPE and Laboratorio ELEA - Argentina. It is supplied in tablets strengths of 12.5, 50 and 100 mg, administered twice daily at a dose of 5 mg/kg body weight/day for adults and 5-10 mg/kg body weight/day for children for 30-60 days. Notably, the current regimens with BZN for the treatment of adults with CD likely represent the maximum dosing case scenario in terms of dose, duration and schedule of administration (Chagas expert meeting DNDi. January 2014. GVA).

Doses and duration of treatment for CD have not been evaluated systematically. Current treatment regimens and dosing intervals have been derived from decades-old patient series and with very limited direct comparisons. Data from recently concluded trials suggest existing opportunities for optimisation of the treatment regimens of BZN.

A (Drugs for Neglected Disease initiative) DNDi-sponsored Phase 2, proof-of-concept clinical trial on E1224 and Benznidazole (BZN) in adults with chronic indeterminate CD, conducted between 2011 and 2013 in Bolivia, showed that all BZN-treated patients had cleared parasite DNA after 2 weeks of treatment and 81% sustained the parasite clearance at 12 months after treatment. At end-of treatment (EOT, Day 65), E1224 was found to be efficacious in clearing T. cruzi parasites when compared to placebo. However, at 12 months less than one third of patients sustained parasite clearance. The trial safety data also indicated a proportion of patients (10-20%) who do not complete treatment in conditions of use, the majority due to adverse drug reactions (ADRs) and the long treatment duration.

Taking into consideration the efficacy gap with about 80% sustained response and a tolerability gap, with a proportion of patients (10-20%) who do not complete treatment, two approaches for Chagas treatment optimization are to be pursued:

1. A change in the current adult dosing regimen for BNZ to reduce exposure and improve tolerability while maintaining efficacy; and
2. The development of a combination therapy to improve efficacy while maintaining or improving tolerability. The combination therapy aims to address the efficacy gap and may or may not address tolerability gap.

With regards to the dosing regimen, population-pharmacokinetics studies observed BZN plasma concentrations in children were significantly lower than those previously reported in adults (treated with comparable mg/kg doses). At the same time, all children had parasite clearance, few adverse reactions to the drug. Recent population PK data in adults suggested that the current BZN dosing regimen (2.5 mg/kg/12 h) may lead to overexposure in the majority of patients. Dosing simulations suggested that a BNZ dose of 2.5 mg/kg/24 h would adequately keep BNZ trough plasma concentrations within the recommended target range for the majority of patients. There are also opportunities for evaluation of fixed dose regimens for adult dosing, rather than mg/kg calculations, with increased ease-of-use and potential for improved compliance in scaling up treatment of CD. Intermittent dosing regimens was also evaluated in murine model of chronic CD and in a pilot follow-up trial with 17 adult patients with chronic CD was, with similar parasitological cure rates to standard treatment.

Likewise, several controlled observational trials with BZN, 5 mg/kg/day for 30 or 60 days have shown a reduction in the progression of heart disease serological and sero-negative conversion up to 60% in children and 30% in adults. Different publications showed anti-parasitic efficacy of treatment regimens with 30 and 60 days, and of incomplete treatment of 10 days. Combination therapy is a well-recognized treatment modality in many disease settings, including cancer, cardiovascular disease, and infectious diseases. Several infectious diseases such as tuberculosis, malaria, leprosy, and AIDS only came under control and were effectively treated after introduction of combinations of drugs that utilize different mechanisms of action.

E1224 is a water-soluble monolysine salt form of the ravuconazole (RAV) pro-drug (which is a phosphonooxymethyl ether derivative of RAV). It is a broad-spectrum triazole antifungal.

Pooled safety data for the monolysine prodrug E1224 from Phase 1 and 2 trials indicated that E1224 was generally well tolerated and exhibited a safety profile quite similar to other azoles. Adverse events occurring in greater than 3% of E1224 recipients, with a dose-dependent pattern and at rates higher than those observed in placebo recipients included nausea, abnormalities in liver enzymes, dizziness, anxiety, and contact dermatitis.

Safety evaluations indicated relatively mild, transient, and asymptomatic increases in liver enzymes - completely reversible upon discontinuation of therapy. Phase 1 cardiac safety evaluations showed that E1224 administration did not result in QTc interval prolongation.

Experimental data suggest a positive interaction between BZN and azole compounds for the treatment of Chagas disease.18 A Phase 1 drug-drug interaction trial was designed to assess the pharmacokinetics (PK) and safety interaction of BNZ and E1224 co-administered daily for a total of 54 days (Day 4 to Day 15- E1224 multiple dose 400 mg loading dose once daily for 3 days, followed by maintenance dose 100mg once daily for 9 days (from Day 7 to Day 15); Day 9 BNZ single dose (2.5 mg/kg); and Day 12 to Day 15 BNZ multiple dose (2.5 mg/kg twice daily)). The trial was conducted in Argentina and was concluded in early 2015, with enrolment of 28 healthy male volunteers. Both compounds were well tolerated, in monotherapy and combination. There were no treatment discontinuations or serious adverse events. Transient, minor, non-concomitant increase in bilirubin and liver transaminases occurred in 2 patients in a pattern not suggestive of drug effect. There was no interaction of RAV on BNZ PK and the limited impact of BNZ on RAV PK, suggesting that co-administration of RAV and BNZ may not require any E1224 dosing adaptation. The lack of clinically relevant safety findings provided support for follow-up evaluation of the two compounds in combination.

In conclusion, recent scientific advances have provided further impetus to develop new therapeutic approaches for CD using different doses and duration of BZN, as well as combinations directed at multiple therapeutic targets to improve treatment response and tolerability and reduce the potential for development of resistance.

This project focuses on the proof-of-concept evaluation of improved treatment regimens of BZN, with the assessment of new BZN-sparing regimens in monotherapy and in combination with E1224.