Part 2: Mucormycosis: Focus on Therapy

INTRODUCTION

Mucormycosis (MCR) a rare but life-threatening infection occurs primarily in immunocompromised hosts. Mortality rates with invasive MCR are high (>30-50%), up to 90% with disseminated disease, but lower (10-30%) with localized cutaneous disease. Due to the rarity of MCR, randomized, controlled therapeutic trials are lacking. Lipid formulations of amphotericin B (LFAB) are the mainstay of therapy but oral triazoles (posaconazole and isavuconazole) may be effective as step-down therapy or in MCR cases refractory to or intolerant of LFAB. Early surgical debridement or excision play important adjunctive roles in localized invasive disease. Control of hyperglycemia in diabetic patients, correction of neutropenia and reduction of immunosuppressive therapy is critical for optimal survival.

AREAS COVERED

The authors discuss various therapeutic options for mucormycosis. A literature search of mucormycosis therapies was performed via PubMed (up to December 2022), using the key words: invasive fungal infections; mold; mucormycosis; Mucorales; amphotericin B; isavuconazole; posaconazole.

EXPERT OPINION

Randomized, controlled therapeutic trials are lacking. Lipid formulations of amphotericin B (LFAB) are the mainstay of therapy but oral triazoles (posaconazole and isavuconazole) may be effective as step-down therapy, in MCR cases refractory to or intolerant of LFAB. We encourage early surgical debridement or excision as adjunctive measures.

Effect of posaconazole on the concentration of intravenous and oral cyclosporine in patients undergoing hematopoietic stem cell transplantation

PURPOSE

This study aimed to investigate the interactions between posaconazole (POS) and intravenously/orally administered cyclosporine A (CsA) in allogeneic hematopoietic stem cell transplant (HSCT) recipients.

METHODS

We included 118 allogeneic HSCT patients who received CsA and POS simultaneously between January 2017 and June 2020 in this study. The ratio of CsA blood concentration (ng/mL) to dosage (mg/day) (C/D) before and after POS initiation was compared.

RESULTS

After the initiation of POS, the level of CsA increased 1 to 2 times in 66% (78/118) of patients compared to those without POS. However, the CsA C/D ratio increased by more than threefold in 6% (7/118) of patients after POS initiation, with an increase of more than fourfold in two patients. The median C/D ratio of CsA increased from 0.89 to 1.23 (P < 0.001) and 0.78 to 1.22 (P < 0.001) after POS initiation when CsA was administered intravenously and orally, respectively. In patients who received POS at the time of transition from intravenous to oral CsA, the value increased from 1.01 to 1.38 (P = 0.001). The route of administration had no significant effect on the change in the CsA C/D ratio (P = 0.615). Additionally, we observed the time required for the C/D ratio to reach a plateau after POS initiation was similar on days 13, 8, and 15 under various scenarios.

CONCLUSION

POS treatment increased blood CsA levels. A large variability was found in the fold-change in the CsA C/D ratio. Therefore, CsA doses should be adjusted by closely monitoring the blood levels of CsA after POS initiation.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Comparative effects of fluconazole, posaconazole, and isavuconazole upon tacrolimus and cyclosporine serum concentrations

INTRODUCTION

Calcineurin inhibitors are commonly used in hematopoietic stem cell transplant (HSCT) patients to prevent graft versus host disease, but as CYP3A4 substrates they are frequently involved in drug-drug interactions. The purpose of this study is to characterize the effects of isavuconazole, fluconazole, and posaconazole on tacrolimus and cyclosporine serum concentrations and dose adjustments in allogeneic HSCT patients.

METHODS

This retrospective study included patients admitted to Oregon Health and Science University between April 2008 and December 2018 who underwent hematopoietic stem cell transplantation and received concomitant tacrolimus or cyclosporine and fluconazole, isavuconazole or posaconazole therapy. Data on patient characteristics, drug dosing, and serum drug concentrations were collected through chart review, and descriptive statistics were used to summarize the results.

RESULTS

A total of 139 patients were included in this study. We found fluconazole initiation leads to a 25% reduction in both tacrolimus and cyclosporine doses in order to maintain goal serum concentrations. Posaconazole and isavuconazole initiation requires tacrolimus dose reductions by 53% and 21%, respectively.

CONCLUSIONS

Based on our experience, FLC, POS, and ISA initiation may require CNI dose reductions and close monitoring of CNI levels to ensure levels remain within goal serum concentrations. Larger studies are needed to fully quantify the percentage in CNI dose reductions and characterize differences among these antifungals.

Initial tacrolimus weight-based dosing strategy in allogeneic hematopoietic stem-cell transplantation

Tacrolimus is a mainstay medication for graft-versus-host disease (GVHD) prophylaxis in combination with other immunosuppressive agents. Achieving therapeutic tacrolimus levels is vital in preventing acute GVHD (aGVHD), while supratherapeutic levels may increase risk of toxicity and relapse. We performed a single center retrospective chart review including all adult patients post-allogeneic hematopoietic stem-cell transplantation who received initial tacrolimus continuous intravenous infusion for GVHD prophylaxis between June 1, 2017 and December 31, 2019. The primary outcome was the percent of patients with an initial therapeutic tacrolimus level, defined as 5-12 ng/mL, after empiric weight-based dosing at 0.02 mg/kg/day. Secondary outcomes included evidence of tacrolimus toxicity within seven days of initiation, incidence of aGVHD by day 100, and relapse after six months. An initial therapeutic level was achieved in 47% of patients with a median initial level of 12.4 ng/mL. Fifty-two percent of patients had supratherapeutic levels. No significant nephrotoxicity, hepatotoxicity, or neurotoxicity occurred within a week of starting tacrolimus or at neutrophil engraftment. Grade II-IV aGVHD by day 100 was observed in 22% of patients, and relapse after six months was found in 16% of patients. These results have led to consideration of an empiric 20% dose reduction to 0.016 mg/kg/day or an expanded initial tacrolimus target of 5-15 ng/mL as there was low aGVHD incidence and no increased risk of toxicity.