Drug-Induced Progressive Multifocal Leukoencephalopathy (PML): A Systematic Review and Meta-Analysis

INTRODUCTION

Progressive multifocal leukoencephalopathy (PML) was first described among patients affected by hematological or solid tumors. Following the human immunodeficiency virus (HIV) epidemic, people living with HIV have represented most cases for more than a decade. With the diffusion of highly active antiretroviral therapy, this group progressively decreased in favor of patients undergoing treatment with targeted therapy/immunomodulators. In this systematic review and meta-analysis, the objective was to assess which drugs are most frequently related to PML development, and report the incidence of drug-induced PML through a meta-analytic approach.

METHODS

The electronic databases MEDLINE, EMBASE, ClinicalTrials.gov, Web of Science and the Canadian Agency for Drugs and Technologies in Health Database (CADTH) were searched up to May 10, 2022. Articles that reported the risk of PML development after treatment with immunomodulatory drugs, including patients of both sexes under the age of 80 years, affected by any pathology except HIV, primary immunodeficiencies or malignancies, were included in the review. The incidence of drug-induced PML was calculated based on PML cases and total number of patients observed per 100 persons and the observation time. Random-effect metanalyses were conducted for each drug reporting pooled incidence with 95% confidence intervals (CI) and median (interquartile range [IQR]) of the observation time. Heterogeneity was measured by I2 statistics. Publication bias was examined through funnel plots and Egger's test.

RESULTS

A total of 103 studies were included in the systematic review. In our analysis, we found no includible study reporting cases of PML during the course of treatment with ocrelizumab, vedolizumab, abrilumab, ontamalimab, teriflunomide, daclizumab, inebilizumab, basiliximab, tacrolimus, belimumab, infliximab, firategrast, disulone, azathioprine or danazole. Dalfampridine, glatiramer acetate, dimethyl fumarate and fingolimod show a relatively safe profile, although some cases of PML have been reported. The meta-analysis showed an incidence of PML cases among patients undergoing rituximab treatment for multiple sclerosis (MS) of 0.01 cases/100 persons (95% CI - 0.08 to 0.09; I2 = 20.4%; p = 0.25) for a median observation period of 23.5 months (IQR 22.1-42.1). Treatment of MS with natalizumab carried a PML risk of 0.33 cases/100 persons (95% CI 0.29-0.37; I2 = 50%; p = 0.003) for a median observation period of 44.1 months (IQR 28.4-60) and a mean number of doses of 36.3 (standard deviation [SD] ± 20.7). When comparing data about patients treated with standard interval dosing (SID) and extended interval dosing (EID), the latter appears to carry a smaller risk of PML, that is, 0.08 cases/100 persons (95% CI 0.0-0.15) for EID versus 0.3 cases/100 persons (95% CI 0.25-0.34) for SID.

CONCLUSIONS

A higher risk of drug-related PML in patients whose immune system is not additionally depressed by means of neoplasms, HIV or concomitant medications is found in the neurological field. This risk is higher in MS treatment, and specifically during long-term natalizumab therapy. While this drug is still routinely prescribed in this field, considering the efficacy in reducing MS relapses, in other areas it could play a smaller role, and be gradually replaced by other safer and more recently approved agents.

Differentiation of highly pathogenic strains of human JC polyomavirus in neurological patients by next generation sequencing

BACKGROUND

JC polyomavirus (JCPyV) persists asymptomatic in more than half of the human population. Immunocompromising conditions may cause reactivation and acquisition of neurotropic rearrangements in the viral genome, especially in the non-coding control region (NCCR). Such rearranged JCPyV strains are strongly associated with the development of progressive multifocal leukoencephalopathy (PML).

METHODS

Using next-generation sequencing (NGS) and bioinformatics tools, the NCCR was characterized in cerebrospinal fluid (CSF; N = 21) and brain tissue (N = 16) samples from PML patients (N = 25), urine specimens from systemic lupus erythematosus patients (N = 2), brain tissue samples from control individuals (N = 2) and waste-water samples (N = 5). Quantitative PCR was run in parallel for diagnostic PML samples.

RESULTS

Archetype NCCR (i.e. ABCDEF block structure) and archetype-like NCCR harboring minor mutations were detected in two CSF samples and in one CSF sample and in one tissue sample, respectively. Among samples from PML patients, rearranged NCCRs were found in 8 out of 21 CSF samples and in 14 out of 16 brain tissue samples. Complete or partial deletion of the C and D blocks was characteristic of most rearranged JCPyV strains. From ten CSF samples and one tissue sample NCCR could not be amplified.

CONCLUSIONS

Rearranged NCCRs are predominant in brain tissue and common in CSF from PML patients. Extremely sensitive detection and identification of neurotropic viral populations in CSF or brain tissue by NGS may contribute to early and accurate diagnosis, timely intervention and improved patient care.

JC Polyomavirus whole genome sequencing at the single molecule level reveals emerging neurotropic populations in Progressive Multifocal Leucoencephalopathy

BACKGROUND

JC polyomavirus (JCV) mostly causes asymptomatic persistent renal infections but may give rise in immunosuppressed patients to neurotropic variants which replicate in the brain causing progressive multifocal leukoencephalopathy (PML). Rearrangements in the JCV genome regulator non-coding control region (NCCR) and missense mutations in the viral capsid VP1 gene differentiate neurotropic variants from virus excreted in urine.

METHODS

To investigate intra-host emergence of JCV neurotropic populations in PML, we deep sequenced JCV whole genome recovered from cerebrospinal fluid (CSF) and urine samples from 32 HIV- and non HIV-infected PML patients at the single-molecule level.

RESULTS

JCV strains distributed among 6 out of 7 known genotypes. Common patterns of NCCR rearrangements included an initial deletion mostly located in a short 10-nucleotide sequence, followed by duplications/insertions. Multiple NCCR variants present in individual CSF samples shared at least one rearrangement suggesting they stemmed from a unique viral population. NCCR variants independently acquired single or double PML-specific adaptive VP1 mutations. NCCR variants recovered from urine and CSF displayed opposite deletion or duplication patterns in binding sites for transcription factors.

DISCUSSION

Long read deep sequencing shed light on emergence of neurotropic JCV populations in PML.

Mutations in the John Cunningham virus VP1 gene could predispose to the development of progressive multifocal leukoencephalopathy in multiple sclerosis patients undergoing treatment with natalizumab

BACKGROUND

Patients with Multiple Sclerosis (MS) undergoing treatment with natalizumab (NTZ) are at risk of developing progressive multifocal leukoencephalopathy (PML) due to the reactivation of John Cunningham (JC) virus. A relevant characteristic among PML cases is the development of single nucleotide mutations in the VP1 gene of the causal JC virus. The identification of such mutations in timely manner can provide valuable information for MS management.

OBJECTIVE

To identify mutations along the JC virus VP1 gene in MS patients undergoing treatment with NTZ, and correlate them with anti-JC virus antibody index.

METHODS

Eighty-eight MS patients, one hundred twenty controls, and six patients with diagnosis of Human Immunodeficiency Virus (HIV) with and without secondary PML were included. JC virus was identified in peripheral blood mononuclear cells and cerebrospinal fluid by PCR. Amplification and sequencing of the entire length of the VP1 gene were performed in all positive clinical samples.

RESULTS

In MS cases no mutations were observed in the JC virus VP1 gene, but it was positive in HIV controls with PML. Interestingly, the JC virus VP1 gene sequence derived from the HIV patients exhibited a non-silent substitution in position 186 (G → C), leading to an amino acid change (Lys → Asp). We did not find correlation between anti-JC virus antibody index and DNA viral detection.

CONCLUSIONS

. The identification of single nucleotide mutants in the JC virus VP1 gene might be an early predictive marker to PML for efficient patient treatment and follow-up.

Exploring the role of NCCR variation on JC polyomavirus expression from dual reporter minicircles

JC virus (JCV), a ubiquitous human polyomavirus, can cause fatal progressive multifocal leukoencephalopathy (PML) in immune compromised patients. The viral genome is composed of two conserved coding regions separated by a highly variable non-coding control region (NCCR). We analyzed the NCCR sequence from 10 PML JCV strains and found new mutations. Remarkably, the NCCR f section was mutated in most cases. We therefore explored the importance of this section in JCV expression in renal (HEK293H) and glioblastoma (U-87MG) cell lines, by adapting the emerging technology of DNA minicircles. Using bidirectional fluorescent reporters, we revealed that impaired NCCR-driven late expression in glioblastoma cells was restored by a short deletion overlapping e and f sections. This study evidenced a relevant link between JCV NCCR polymorphism and cell-type dependent expression. The use of DNA minicircles opens new insights for monitoring the impact of NCCR variation.

Classifying PML risk with disease modifying therapies

OBJECTIVE

To catalogue the risk of PML with the currently available disease modifying therapies (DMTs) for multiple sclerosis (MS).

BACKGROUND

All DMTs perturb the immune system in some fashion. Natalizumab, a highly effective DMT, has been associated with a significant risk of PML. Fingolimod and dimethyl fumarate have also been unquestionably associated with a risk of PML in the MS population. Concerns about PML risk with other DMTs have arisen due to their mechanism of action and pharmacological parallel to other agents with known PML risk. A method of contextualizing PML risk for DMTs is warranted.

METHODS

Classification of PML risk was predicated on three criteria:: 1) whether the underlying condition being treated predisposes to PML in the absence of the drug; 2) the latency from initiation of the drug to the development of PML; and 3) the frequency with which PML is observed.

RESULTS

Among the DMTs, natalizumab occupies a place of its own with respect to PML risk. Significantly lesser degrees of risk exist for fingolimod and dimethyl fumarate. Whether PML will be observed with other DMTs in use for MS, such as, rituximab, teriflunomide, and alemtuzumab, remains uncertain.

DISCUSSION

A logical classification for stratifying DMT PML risk is important for both the physician and patient in contextualizing risk/benefit ratios. As additional experience accumulates regarding PML and the DMTs, this early effort will undoubtedly require revisiting.

Natalizumab-treated patients at high risk for PML persistently excrete JC polyomavirus

Sixty-three natalizumab-treated patients with relapsing multiple sclerosis were screened for JC polyomavirus (JCV) viruria. Urinary-positive patients were longitudinally sampled for up to 24 weeks. Using methods that distinguish encapsidated virus from naked viral DNA, 17.5 % of patients were found to excrete virus, consistent with the prevalence of urinary excretion in the general population. Unexpectedly, urinary excretion was predominantly seen (>73 %) in patients with high JC antibody index (≥2.0). Active JCV infection, therefore, tends to occur in natalizumab patients that carry a high risk factor for the development of disease, directly linking JC infection to the risk factors for PML development.

High cumulative JC virus seroconversion rate during long-term use of natalizumab

BACKGROUND AND PURPOSE

John Cunningham virus (JCV) seropositivity is a risk factor for the development of natalizumab-associated progressive multifocal leukoencephalopathy (PML) in multiple sclerosis (MS) patients. When JCV seronegative patients seroconvert, their risk of developing PML increases. Limited longitudinal data exist about the seroconversion rate amongst natalizumab-treated relapsing-remitting MS (RRMS) patients. Our objective was to evaluate the seroconversion rate in a large Dutch cohort of natalizumab-treated RRMS patients. Seroconversion was defined as at least two consecutive seropositive serum samples (or cessation of therapy after a single seropositive sample because of seropositivity) after initial seronegative testing.

METHODS AND RESULTS

In our study of 179 patients for whom longitudinal blood samples were available over a long period (median 4.2 years), anti-JCV antibody indices were measured in 933 available samples. Eighty-six patients (48.0%) tested seronegative initially. Of these 86 seronegative patients, 23 patients (26.7%) seroconverted during follow-up. The annualized seroconversion rate was 7.1%. Seroconversion occurred between 9 and 90 months (median 43 months) of treatment. The rate of seroconversion was independent of follow-up duration. No significant increase was seen in the anti-JCV antibody index in the non-converting patients during the follow-up.

CONCLUSION

The annualized seroconversion rate of 7.1% in patients using natalizumab, cumulatively leading to more than 25% of seronegative patients becoming seropositive in 4 years, is of clinical relevance and should be taken into account in the risk assessment when considering the start of natalizumab therapy.