Anifrolumab, a potential treatment for ADA2 deficiency

Abstract

Adenosine deaminase 2 deficiency (DADA2) is an inborn error of immunity leading to systemic vasculitis, haematological manifestations, immune deficiency and/or autoimmunity. We report the case of a 26-year-old female with an initial diagnosis of systemic lupus erythematosus (SLE). However, atypical evolution patterns for SLE (hypogammaglobulinaemia, moderate B-cell lymphopenia, disappearance of anti-dsDNA) led to the identification of a homozygous class 5 missense variant of CECR1/ADA2, thus to a final diagnosis of DADA2. Strikingly, the patient was treated with anifrolumab (an anti-interferon alpha receptor 1 antibody) that rapidly induced clinical remission and significant corticosteroid tapering. Consistently, we show a lower type I interferon (IFN-I) score and a persistently low tumour necrosis factor α (TNFα) and IL-6 expression levels in whole blood cells of the patient during anifrolumab compared to anti-TNFα. Altogether, this case (1) illustrates the challenging diagnosis of DADA2 (SLE with hypogammaglobulinaemia) and (2) reinforces DADA2 as a disease at the border with type I interferonopathies. Besides, we report here, to our knowledge, the first description of a successful use of anifrolumab in DADA2, paving the way for further studies to validate this therapeutic approach.

Introduction

Adenosine deaminase 2 deficiency (DADA2) is an inborn error of immunity leading to a broad spectrum of clinical phenotypes such as systemic vasculitis, haematological manifestations and/or immune deficiency.¹ Interestingly, DADA2 patients can also display autoimmune-like features, including systemic lupus erythematosus (SLE).² Management of DADA2 patients is relatively straightforward for vasculitis/vasculopathy; anti-tumour necrosis factor α (anti-TNFα) therapy has been shown to be efficient in treating vasculitis and in preventing strokes.³ However, treatment gaps remain evident regarding immunodeficiency, autoimmunity and haematological manifestations.

We report here the case of a mid-20s female DADA2 patient with SLE-like phenotype, successfully treated with anifrolumab (an anti-interferon α receptor 1 antibody (anti-IFNAR1) leading to remission of clinical symptoms and efficient corticosteroid sparing.

Clinical case and biological evaluation

A mid-20s female patient was referred to our hospital in 2018 for the follow-up of an SLE. First symptoms appeared at the age of 19 years with a compensated warm antibody autoimmune haemolytic anaemia, leuconeutropenia, fever, Raynaud’s phenomenon, photosensitivity, arthritis and splenomegaly. Notably, parents were related. No autoimmunity was reported in first-degree relatives. Initial biological autoimmune screening showed speckled anti-nuclear antibodies at a titre of 640 with positive anti-double stranded DNA antibodies (anti-dsDNA). Anti-extractable nuclear antigen antibodies and antiphospholipid antibodies were negative. Complement evaluation was normal. Based on American College of Rheumatology/European Alliance of Associations for Rheumatology 2019 criteria, a diagnosis of haematologic, rheumatologic and cutaneous SLE was made.⁴

Initial therapeutic approaches involved hydroxychloroquine 5 mg/kg/day and low dose corticosteroids. Due to inflammatory articular flares, methotrexate 0.3 mg/kg/week, azathioprine 2 mg/kg/day and belimumab—anti B-cell activating factor antibody—200 mg/week were successively administered over a 5-year period but were later discontinued because of side effects and/or insufficient corticosteroid sparing. In this clinical context, the detection of an elevated type I interferon (IFN-I) score at 7.4 (n<2.3) advocated for the initiation of anifrolumab—an anti-IFNAR1—at 300 mg monthly.

In parallel, meticulous reading of the patient’s biological follow-up showed appearance of hypogammaglobulinaemia predominating on IgG2 and IgM (1254 mg/L and 0.10 g/L, respectively), moderate B-cell lymphopenia, disappearance of anti-dsDNA and elevated CH50. These biological hallmarks collectively advocated for atypical SLE evolution. Thus, genetic assessment was performed and remarkably identified a homozygous class 5 missense variant of CECR1/ADA2 in c. 578C>T, p.(Pro193Leu), which was already described as hypomorphic in transfection assay.⁵ After confirmation of the absence of ADA2 enzymatic activity, a final diagnosis of ADA2 deficiency (DADA2) was made. Treatment was switched for adalimumab—anti-TNFα—40 mg/kg/week, according to current recommendations for the treatment of DADA2.¹

Figure 1A successively presents clinical effects, biological effects and corticosteroid-sparing effects of anifrolumab and adalimumab in our patient. Strikingly, anifrolumab allowed clinical remission (regression of initial skin lesions, inflammatory arthralgia, polyarthritis and asthenia), normalisation of lymphopenia, as well as significant corticosteroid tapering (threshold of corticodependence decreased from 40 mg/day to 7 mg/day of prednisone). In contrast, after switching anifrolumab for adalimumab, our patient displayed clinical articular flares that led to a novel increase of prednisone up to 20 mg/day. However, under adalimumab, skin lesions and asthenia were still well controlled and hypogammaglobulinaemia reverted to normal. Simultaneously, figure 1B presents RNA expression profiles including IFN-I score, TNFα, interleukin 6 (IL-6) and interleukin 1 (IL-1) in whole blood cells of the patient before and during anifrolumab as well as during adalimumab. We show a lower IFN-I score and persistently low TNFα and IL-6 expression levels during anifrolumab compared with adalimumab. Interestingly, IL-1 expression increased during anifrolumab in comparison with conventional immunosuppressants or adalimumab.

Figure 1. (A) Evolution of clinical and biological parameters as well as steroids treatment before, during anifrolumab and during adalimumab treatment. Green background illustrates normal or improved parameters and red background indicates abnormal or deteriorated parameters. (B) Evolution of type I interferon (IFN-I), interleukin 1 (IL-1), IL6 and tumour necrosis factor α (TNFα) scores before, during anifrolumab and during adalimumab treatment. ANA, anti-nuclear antibodies; CRP, C-reactive protein; LDH, lactate dehydrogenase.

Discussion

From a clinical point of view, DADA2 can exhibit 3 main presentations: (1) autoinflammation with vasculitis, livedo and strokes, (2) haematological manifestations with red cell aplasia and hypogammaglobulinaemia leading to recurrent infections as well as (3) autoimmunity. Regarding autoimmune manifestations, DADA2 can present as SLE, being part of the monogenic lupus spectrum.⁶ Alternatively, IFN-I score, one of the biological hallmarks of SLE, is increased among DADA2 patients.⁷

We report here the case of a mid-20s female patient with SLE-like phenotype that was diagnosed with DADA2 6 years after being referred to our centre. Careful examination of clinical and biological signs during her follow-up, as well as inefficiency of conventional therapies, urged us to look for a differential diagnosis. Genetic assays for SLE-like conditions eventually led to the diagnosis of DADA2.

Furthermore, we suggest that anifrolumab is an efficient therapeutic approach, leading to clinical remission and to corticosteroid sparing. After DADA2 diagnosis, we switched the treatment for adalimumab (standard of care) as it is currently the only one preventing vasculopathy in the disease.^{1 3} Strikingly, our patient presented new articular flares under adalimumab, whereas there were no articular manifestations under anifrolumab.

Pathophysiology of DADA2 is not yet fully understood. Formerly, lack of extracellular activity of adenosine deaminase by ADA2 was thought to be the pathogenic mechanism of autoimmune and autoinflammatory manifestations. However, another adenosine deaminase, ADA1, seems to be able to perform this extracellular role and compensate ADA2.⁸ New evidence shed light on the role of ADA2-mediated nucleic acid editing leading to Toll-Like Receptor 9 (TLR9) modulation and IFN-I response.^{9 10} Indeed, the TLR9-MyD88 signalling plays a critical role in the upregulation of proinflammatory cytokines, including IFN-I, IL6 and TNFα via NF-κB activation.^{1 11} Our analysis of IFN-I score, IL6 and TNFα RNA expression profiles is consistent with this data. Furthermore, we suggest that anifrolumab can successfully decrease IFN-I, IL6 and TNFα scores, aligning with the patient clinical remission. Interpretation of IL1 expression levels is more challenging, but an increase of IL1 expression under IFNAR1 blocking antibody could be explained by the loss of inhibition of the IFN-I pathway on IL1 activity.¹²

To conclude, this case (1) illustrates the challenging diagnosis of DADA2 (SLE-like with hypogammaglobulinaemia) and (2) reinforces DADA2 as a disease at the border with type I interferonopathies.⁶ Besides, we report here, to our knowledge, the first description of a successful use of anifrolumab in DADA2, paving the way for further studies to validate this therapeutic approach.

Material and methods

Patient and genetic analysis

Written informed consent was obtained from the proband. This study was conducted in accordance with French legislation, Good Clinical Practice and the Declaration of Helsinki.

DNA was extracted from whole blood sample. PCR sequencing was performed using the Twist hereditary immune deficiencies panel library of the Study Center of Immune Deficiency and sequencing was performed using the Illumina NextSeq 500 platform. The variant was annotated on the ADA2 NM_001282225 transcript.

RNA extraction

Total RNA extraction was performed on whole blood collected on EDTA or PaxGene using a Maxwell 16 LEV SimplyRNA Blood Kit (Promega) and a magnetic particle processor (Maxwell 16; Promega) according to the manufacturer’s recommendations. The extraction kit included an individual DNAse treatment. Total RNA was diluted in 40 µL RNAse-free water, and concentration was quantified by spectrophotometry using a NanoVue (Biochrom).

IFN-I, IL6, TNFα and IL1 scores

The NanoString-based protocol for the interferon score was previously published. The expression of 6 Interferon Stimulated Genes (ISGs)—SIGLEC1, IFI27, IFI44L, IFIT1, ISG15 and RSAD2—was measured for the IFN-I score. IL6 transcript, TNFα and IL1 transcripts were used for each eponymous score.

For each score, the absolute count of each transcript was normalised by the geometric mean of the counts from three reference genes: ACT (β-actin), HPRT1 (hypoxanthine phosphoribosyltransferase 1) and RNA polymerase II subunit A. The relative expression score was determined by dividing the normalised expression of each ISG by the median of its expression in 34 healthy donors.