Progression of human monkeypox infection despite tecovirimat in an immunocompromised adult

Challenges in Managing Treatment-Resistant Mpox Complicated by Severe Superinfection

Though typically self-limiting, severe mpox infections have been treated with antiviral medications, most notably tecovirimat. Various reports exist of mpox progression despite tecovirimat treatment. Treatment resistance can be due to acquired mpox strain mutations, most often occurring in an immunocompromised host. We present the case of a male with AIDS who developed disseminated treatment-resistant mpox infection complicated by superimposed bacterial and fungal infections. His orthopoxvirus polymerase chain reaction result remained positive despite treatment with 4 weeks of oral tecovirimat and 3 doses of intravenous cidofovir. Poor response to antiviral therapy was likely due to his underlying immunocompromised state; however, strain resistance cannot be ruled out given that the patient had started but not completed a 14-day course of tecovirimat 8 months prior, at the time of initial mpox diagnosis. Patients with mpox who are immunocompromised may require extended and additional treatment beyond the standard 14 days of tecovirimat, such as cidofovir, brincidofovir, or intravenous vaccina immune globulin.

Tecovirimat Resistance in Mpox Patients, United States, 2022-2023

During the 2022 multinational outbreak of monkeypox virus (MPXV) infection, the antiviral drug tecovirimat (TPOXX; SIGA Technologies, Inc., https://www.siga.com) was deployed in the United States on a large scale for the first time. The MPXV F13L gene homologue encodes the target of tecovirimat, and single amino acid changes in F13 are known to cause resistance to tecovirimat. Genomic sequencing identified 11 mutations previously reported to cause resistance, along with 13 novel mutations. Resistant phenotype was determined using a viral cytopathic effect assay. We tested 124 isolates from 68 patients; 96 isolates from 46 patients were found to have a resistant phenotype. Most resistant isolates were associated with severely immunocompromised mpox patients on multiple courses of tecovirimat treatment, whereas most isolates identified by routine surveillance of patients not treated with tecovirimat remained sensitive. The frequency of resistant viruses remains relatively low (<1%) compared with the total number of patients treated with tecovirimat.

Emerging pharmacological strategies for treating and preventing mpox

INTRODUCTION

Since May 2022, there have been nearly 87,000 documented cases of mpox worldwide, with 119 deaths. Pharmacological interventions for mpox include the MVA-BN smallpox vaccine, tecovirimat, cidofovir, its pro-drug brincidofovir, and vaccinia immune globulin intravenous (VIGIV).

AREAS COVERED

The literature search and information gathering for this review included the PubMed database focusing on mpox and monkeypox, in combination with tecovirimat, brincidofovir, cidofovir, VIGIV, and smallpox vaccine. WHO.int, CDC.gov, FDA.gov, and ClinicalTrials.gov websites were accessed for the most recent information on the mpox outbreak. Mechanisms for deployment and access to treatment including expanded access, emergency use, and clinical trials will be discussed. Treatment outcomes with safety data will be presented.

EXPERT OPINION

The vaccine as a preventive measure, along with numerous treatment options, largely controlled the outbreak, although deployment of each could be improved upon to hasten and broaden access. More widespread coverage by the vaccine is necessary to prevent future resurgence of mpox. Tecovirimat has emerged as a safe frontline treatment for mpox, while brincidofovir use has been limited by safety concerns. VIGIV and cidofovir should be reserved for the most severe cases in which other options are not fully effective.

Monkeypox (mpox) in immunosuppressed patients

The World Health Organization (WHO) proclaimed a public health emergency in July 2022 due to the emergence of Mpox (formerly monkeypox) while the globe was still dealing with the COVID-19 epidemic. The characteristics of mpox in immunocompetent individuals are well-characterized, despite difficulties in diagnostics, immunization, and access to treatment that persist in low-income countries. Patients with weakened immune systems are more likely to spread an illness and die from it than healthy people because they cannot mount a protective immune response against it, such as a neutralizing IgG and poxvirus-specific Th1 response. A health warning on severe mpox in people who are immunocompromised due to Human Immunodeficiency virus (HIV) and other illnesses was released by the U.S. Centers for Disease Control and Prevention (CDC) on September 29, 2022. The advice does not specifically include primary immunodeficiency, but it does define other immunocompromising disorders as “having autoimmune disease with immunodeficiency as a clinical component”. Both those with healthy immune systems and those with weakened immune systems, such as those who are immunosuppressed, older people, children, etc., have encountered serious health issues, but the latter group is more likely to do so. According to the advisory, “of the people with severe mpox manifestations for whom CDC has been consulted, the majority have had HIV with CD4 counts 200 cells/ml, indicating substantial immunosuppression”. However, new cases are still expected to be discovered, especially in low-income countries with limited access to diagnosis, treatment, and prevention, and where a large percentage of the mpox-infected population also has advanced HIV infection. Thus, further research is always needed to determine the best way to treat mpox in immunocompromised people. In this context, we discussed /reviewed the mpox clinical presentation, available treatment options and current preventive guidelines in immunocompromised patients.