Rituximab Therapy for Immune-Mediated Neurological Diseases: Our Experience at a Tertiary Care Centre

Introduction: Rituximab (RTX) is a monoclonal anti-CD20 chimeric antibody that inhibits B cell activity. However, it is an appealing substitute for traditional immunomodulatory drugs as a swiftly acting, targeted therapy with mounting evidence of efficacy and tolerance in numerous neuroinflammatory conditions. We discuss the scientific evidence for the use of RTX in neurological illnesses, as well as the dose, safety, and other practical elements of prescription. Aim: This study aims to assess and correlate the effects of RTX on immune-mediated neurological disorders. Objectives: The primary objective of this study is to determine the outcomes in patients treated with RTX for the following conditions: myasthenia gravis (MG), autoimmune encephalitis, multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein antibody disease (MOGAD), immune-mediated peripheral neuropathy, and inflammatory muscle disease. The secondary objective is to assess adverse drug reactions in patients treated with RTX. Methods: This is a prospective observational study conducted at a tertiary care centre. The data were analyzed for the period from May 2022 to May 2024. Approval was obtained from the institutional ethics committee before commencing the study, and written informed consent was obtained from all patients. Results and conclusions: A total of 56 patients were included in the study. The distribution of patients according to diseases is as follows: MG (17), MS (11), NMOSD (10), MOGAD (7), immune-mediated peripheral neuropathy (6), autoimmune encephalitis (3), and inflammatory muscle disease (2). However, one patient was lost to follow-up in the autoimmune encephalitis group. All patients experienced improvements in symptoms, and no relapse episodes have been reported except for one patient who had a relapse in the inflammatory muscle disease group. During the infusion process, some adverse drug reactions, such as chills and rigors, were observed, and two patients experienced major side effects, such as Pott's disease and cryptogenic organizing pneumonia. Nevertheless, overall, rituximab shows promise as an off-label immunosuppressive treatment for the aforementioned neurological immune-mediated diseases.


Introduction
Rituximab (RTX) is a chimeric antibody that acts as an inhibitor of B cells by targeting CD20 [1,2].In 1980, RTX was first administered to a patient with lymphoma by Lee Nadler at the Dana-Farber Cancer Institute using the Köhler-Milstein technique [3,4].Antibodies can be classified into various immunoglobulin classes (M, G, D, E, or A) and subclasses (such as IgG1-4).Additionally, these antibodies are linked with immunemediated neurological diseases [5].For the past 11 years, RTX has been extensively utilized as an off-label therapy for individuals with multiple sclerosis (MS) and has shown reduced relapse rates and disability progression in MS.Additionally, RTX has been used off-label for other immune-mediated neurological diseases mentioned above.
Beneficial outcomes have been documented in terms of reducing relapses and decreasing the development of the disease.Crucially, a sizable observational study of Swedish MS patients revealed no significant side effects from its sustained use [6].Many other trials from different nations have validated the safety and effectiveness of RTX in lowering relapses and disability in neuromyelitis optica spectrum disorder (NMOSD) since Cree et al.'s initial report on the drug's effectiveness in treating the illness [7][8][9].RTX has also shown promising outcomes in cases of myelin oligodendrocyte glycoprotein antibody disease (MOGAD) and immune-mediated peripheral neuropathy [10][11][12].Additionally, RTX has demonstrated promising outcomes in the treatment of autoimmune encephalitis (AE) and inflammatory muscle disease.

Materials And Methods
We conducted a prospective observational study on patients with immune-mediated neurological diseases who presented at a tertiary care hospital in India from May 2022 to May 2024.Approval was obtained from the institutional ethics committee of Dr. D. Y. Patil Medical College, Hospital & Research Centre (IESC/S.SP/01/2022) before commencing the study, and written informed consent was obtained from all patients.The sample size was calculated using the method described for a descriptive prevalence study based on effect size and absolute precision.The minimum sample size for the study was determined to be 30 subjects based on the prevalence of the disease mentioned in prior studies.A total of 56 patients were included in this study.

Inclusion criteria
The study included patients with the following immune-mediated neurological diseases: (1) myasthenia gravis (MG), MS, NMOSD, MOGAD, immune-mediated peripheral neuropathy, inflammatory muscle disease, and AE; (2) all patients willing to give informed consent for their participation in the study; and (3) age more than 18 years old.

Exclusion criteria
Excluded in the study are (1) patients who are not willing to give consent for participation in the study; (2) pregnant women in the first trimester (RTX is relatively safe during pregnancy; however, the first trimester is a critical phase of organogenesis, and there are a few reports that suggest it may cause abortion if used in the first trimester.Complications observed in the second and third trimesters are very rare and manageable); and (3) patients having active infections such as tuberculosis, progressive multifocal leukoencephalopathy, HIV, hepatitis B surface antigen (HbsAg), or hepatitis C virus (HCV) (all chronic infections) were considered in order to prevent a flare-up of such infections.
Relapse was defined by new neurological symptoms or worsening of existing symptoms, which may be associated with worsening observed in laboratory or radiological assessments.Even a mild worsening of symptoms was considered.For example, in the case of MG, an increase in fatigability or worsening in the MGFA (MG-Foundation of America) class or other scales mentioned below; in the case of MS/NMOSD/MOGAD, new neurological symptoms or worsening of existing symptoms associated with radiological worsening; and in the case of other immune-mediated neurological diseases, we monitored them closely using respective scales/scores and also monitored laboratory or radiological parameters.In the event of a relapse, an alternative treatment therapy was considered.

The protocol for RTX infusion at our centre
Written informed consent was obtained from the patients, and the benefits and complications regarding RTX were explained to the patient and their relatives.On the day of RTX infusion, it was important to clinically rule out active infection.Routine blood investigations, including a complete blood count, renal and liver function tests, sero-markers (HIV/HbsAg/HCV), urine routine microscopy, and chest X-ray, were performed.
Before starting RTX infusion, premedication with intravenous 125 mg methylprednisolone and intravenous pantoprazole 40 mg was administered.RTX was slowly administered with an initial infusion rate of 10 mL/hour, increasing every 10 minutes to 150 mL/hour, with cardiac monitoring.A total of 1 g was given in two divided doses, each in 500 mL of normal saline.The induction dose of 1 g RTX was administered 15 days apart, followed by maintenance doses every six months.
For female patients of reproductive age, counseling regarding conception and the risks and benefits of RTX was provided.We explained to patients the importance of planning their pregnancies accordingly and advised them on the timing of RTX doses prior to and just after delivery or in the second or third trimester.

Patient outcomes assessed with various parameters
For MG, outcomes were assessed using the following tools: Quantitative-MG (QMG), MGFA scale, MG-Activities of Daily Living (MG-ADL), MG-Quality of Life-15-revised (MG-QoL-15r), and MG-Composite Scale (MG-CS).For NMOSD, MOGAD, and MS, the Expanded Disability Status Scale (EDSS), Radiological lesions per year, and Fatigability Severity Scale (FSS) were used.For immune-mediated peripheral neuropathy, the Modified Neuropathy Symptoms Score stage (MNSS), FSS, Neuropathy Disability Score (NDS), and Shortened and Revised Total Neuropathy Scoring (SRTNS) were employed.For AE, the Clinical Assessment Scale in AE (CASE), Radiological lesions per year, and Modified Ranking Scale (MRS) were utilized.For inflammatory muscle disease, the creatine phosphokinase-N-acetyl cysteine (CPK-NAC) levels were used.The annual relapse rate (ARR) was considered in all the above conditions.Data were collected from hospital admission records.Follow-up clinical comparative examinations and improvement assessments were conducted every six months until the last follow-up, with additional assessments as needed.MRI scans were performed yearly to detect new lesions.Outcomes were analyzed based on demographic details and the number of doses of RTX, as well as its efficacy in the form of clinical scales, laboratory, radiological improvement, and ARR related to the disease.Safety was assessed in terms of drug infusion-related reactions, as well as consideration of long-term infections or reactivation of infections.

Statistical analysis
Parametric variables, representing normally distributed data, were depicted using both the mean and median.Data were compared from the baseline clinical scales, laboratory results, and radiological patient data to the most recent follow-up.

Results
The study comprised 56 patients, of whom 24 were males and 32 were females.The males had an average age of 49, whereas the females had an average age of 37 (Table 1).

Disease
Frequency

Patients with MG
A total of 17 individuals were diagnosed with MG (10 males and 7 females).Baseline to follow-up comparisons were made for MGFA class, MG-CS, MG-ADL, MG-Qol-15r, and QMG scores that showed significant improvements with an ARR of 0 (

Patients with NMOSD
A total of 10 patients diagnosed with NMOSD underwent RTX treatment, comprising nine females and one male.Radiological lesions at presentation had a mean ± SD and median (IQR) of 4.4 ± 4.0 and 2.5 (2-6.75),respectively, (n=10).At one year (n=8), it was 4.1 ± 4.4 and 2 (0.75-8.25); at two years (n=3), it was 6.0 ± 4.4 and 8 (4.5-8.5).One patient who completed two years of the study had a baseline lesion load of 11, which reduced to nine at two years.Overall, radiological lesions in the above population did not increase, and no new enhancing lesions were observed, showing a significant response to treatment.EDSS showed significant improvement from 3.6 ± 1.3 to 1.5 ± 1.3 (Table 3) (Figure 1).All patients were in the remission phase (ARR=0).NMOSD: neuromyelitis optica spectrum disorder.

Patients with MOGAD
Seven patients diagnosed with MOGAD underwent RTX treatment, with an F:M ratio of 1.3:1 and an average age of 38.3 (±18.9).Radiological lesions at presentation had a mean ± SD and median (IQR) of 3.7 ± 4.7 and 2 (1-3.5),respectively, (n=7).At one year (n=7), it was 4.1 ± 4.4 and 1 (0.75-8.25); at two years (n=4), it was 3.5 ± 5.7 and 1 (0.75-3.75).One patient who completed two years of the study had a baseline lesion load of 14, which reduced to 12 at two years.Overall, radiological lesions in the above population did not increase, and no new enhancing lesions were observed, showing a significant response to treatment.Comparing FSS and EDSS showed significant improvement (Table 4) (Figure 2).All patients were in the remission phase (ARR=0).

Patients with IMD
Two patients in the IMD group received treatment with rituximab, out of which one (50%) had antisynthetase syndrome (anti-PL-7,12 positive), and one (50%) had dermatomyositis (anti-Mi-2 positive), (two females and 0 male; M:F=2:0) with a mean age of 51.0 (±17.0).Comparing CPK-NAC levels from baseline to follow-up showed significant improvement (Table 8).However, the patient with anti-synthetase syndrome (anti-PL-7,12 positive) experienced a relapse and subsequently switched to methotrexate, while the other patient with dermatomyositis responded well until the first maintenance dose.However, three months after the first maintenance dose, the patient developed Pott's spine.An interferon-gamma release assay (IGRA) test (TB-gold test) was done in this patient prior to starting RTX, resulting in the suspension of further subsequent doses of RTX.

Adverse drug reactions
In most patients, infusion-related reactions occurred during the first induction dose.These reactions were manageable by reducing the infusion rate.Afterward, patients tolerated RTX infusion well.Some patients experienced minor side effects, which were effectively managed.However, some patients experienced major side effects, such as one had cryptogenic organizing pneumonia.Another patient developed Pott's spine, in this group of patients [18].In 2021, Uzunköprü et al. demonstrated the efficacy of RTX.The EDSS scores decreased from 3.94 ± 1.98 to 2.67 ± 1.54, and ARR decreased from 1.45 ± 1.53 to 0.15 ± 0.34.No radiological activity was observed or assessed at intervals of one year, which is similar to our study [19].Both the RIN-1 study and the meta-analysis conducted by Gao et al. showcased promising results of RTX in this patient group [20,21].

MOGAD
In January 2023, Nepal et al. conducted a meta-analysis that demonstrated promising results for the offlabel use of RTX for MOGAD, which included 13 studies and 238 patients.The analysis revealed that the ARR was lowered by 1.36 and EDSS by 0.52 [22].In our study, there was a significant reduction in EDSS from 3.

MS
In 2020, Ghajarzadeh et al. conducted a meta-analysis that demonstrated promising results for the off-label use of RTX for MS patients, which included 399 MS patients.The analysis revealed a reduction in EDSS by 0.29 and ARR by 1.24, with no new radiological activity detected.The most commonly reported adverse drug reaction was an infusion-related reaction, similar to our study.EDSS reduced from 3.1 ± 1.3 to 0.5 ± 0.9, and there was no radiological activity [25].In 2008, the HERMES Trial led by Hauser et al. showcased a significant decrease in total gadolinium-enhancing lesions, mirroring findings in our study.As per protocol, we repeated MRI scans every year [26].
In 2021, Fatehi et al. showed substantial improvement with RTX in a patient with CIDP, which aligns with the findings in our study [11].In 2018, a meta-analysis on vasculitic neuropathy conducted by Mena-Vázquez et al. demonstrated significant improvement in functional outcomes and disability, which aligns with our findings in cases of vasculitic neuropathy [12].
RTX also shows promising results in our study with the AE group, where improvement in MRS and CASE scores was observed, with an ARR of 0. Similar to the findings of Thaler et al. in their 2021 study and the meta-analysis published by Nepal et al. in 2020 [27,28].
In 2023, Gamba et al. studied the effectiveness of RTX in inflammatory autoimmune muscle diseases and demonstrated an excellent response, with improvement in CPK-NAC and clinical recovery, along with a significant reduction in ARR.However, in our study, one patient with anti-synthetase syndrome experienced a relapse, while another with dermatomyositis initially responded well to RTX therapy but later developed Pott's spine, leading to the hold of subsequent doses [29].In 2022, Zhen et al. conducted a meta-analysis on idiopathic inflammatory myopathies (IIMs), presenting encouraging outcomes associated with RTX [30].
Our study had a few limitations.Firstly, it had a small sample size.Additionally, it was an observational study conducted at a single tertiary care centre.Furthermore, long-term follow-up is essential.

Conclusions
This present study demonstrates excellent efficacy and a safe therapeutic option for immune-mediated neurological diseases with RTX.Compared to other immunomodulatory therapies, RTX has a generally good safety record.However, further long-term follow-up with a larger study group is necessary to ascertain extended long-term outcomes and establish guidelines for the duration of RTX treatment.This will help identify any potential long-term complications associated with RTX therapy.

Appendices Sample size calculation
Based on a previous study referred to below, with a 95% confidence interval, there is a clinically meaningful difference of 8%, and the prevalence of autoimmune neurologic disorders is 4%.Accounting for a 10% noninclusion or drop-out rate, the minimum required sample size should be 28 participants.After rounding off, the finalized sample size was 30 participants.

FIGURE 1 :
FIGURE 1: Bar diagram showing the efficacy of rituximab in a group of patients with NMOSD.

FIGURE 2 :
FIGURE 2: Bar diagram showing the efficacy of rituximab in a group of patients with MOGAD.MOGAD: myelin oligodendrocyte glycoprotein antibody disease; EDSS: Expanded Disability Status Scale.

FIGURE 3 :
FIGURE 3: Bar diagram showing the efficacy of rituximab in a group of patients with MS.MS: multiple sclerosis; EDSS: Expanded Disability Status Scale.

FIGURE 4 :
FIGURE 4: Bar diagram showing the efficacy of rituximab in a group of patients with IMPN.IMPN: immune-mediated peripheral neuropathy; SRTNS: Shortened and Revised Total Neuropathy Scoring.
3 ± 0.4 to 1.4 ± 1.1, with an ARR of 0, and no new radiological activity was observed.Additionally, other studies by Bai et al. and Barreras et al. have demonstrated positive results in MOGAD patients with RTX treatment, similar to our study[23,24].

TABLE 3 : Efficacy of RTX in a group of patients with NMOSD.
NMOSD: neuromyelitis optica spectrum disorder; EDSS: Expanded Disability Status Scale; IQR: interquartile range; NA: not applicable.

TABLE 4 : Efficacy of RTX in a group of patients with MOGAD.
MOGAD: myelin oligodendrocyte glycoprotein antibody-associated disease; IQR: interquartile range; EDSS: Expanded Disability Status Scale; NA: not applicable.

TABLE 5 : Efficacy of rituximab in a group of patients with MS.
MS: multiple sclerosis; EDSS: Expanded Disability Status Scale; NA: not applicable.

TABLE 7 : Efficacy of rituximab in a group with autoimmune encephalitis.
NMDAR: N-methyl-D-aspartate receptor; CASE: Clinical Assessment Scale in AE; NA: not applicable.