9/19/2020

Macrophage Activation Syndrome Nuances in Presentation and New Therapeutic Targets

Alexei Grom, MD Professor of Pediatrics Cincinnati Children's Hospital Medical Center

OUTLINE

• Brief overview of MAS pathophysiology and classic clinical features • Distinct clinical patterns of MAS • Treatment • new therapeutic targets

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DISCLOSURES

• Consulting fees, research collaborations with Novartis, AB2Bio, NovImmune (Sobi) • North American PI of the clinical trial of emapalumab, an anti-IFNγ monoclonal antibody, in patients with SJIA developing refractory MAS: NCT03311854 (NovImmune/Sobi)

Macrophage Activation Syndrome

• Caused by excessive activation and proliferation of T cells and well-differentiated non-neoplastic macrophages • Macrophages exhibit hemophagocytic activity • Massive systemic inflammatory response associated with • cytopenias • liver dysfunction • coagulopathy consistent with DIC and • extreme hyperferritinemia • Can be fatal (mortality up to 20%) Silverman ED, et al. J Pediatr 1983;103:872. Hadchouel M, Prieur AM, and Griscelli C. J Pediatr 1985;106:561.

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MAS in Pediatric Rheumatology

• Since the original description, MAS has been reported in association with almost any rheumatic disease

• By far, most common in systemic JIA • About 80% of reported cases occurred in association with systemic JIA • SLE, Kawasaki disease • Prevalence of “overt MAS” in systemic JIA is ~7-14% Sawney, et al. Arch Dis Child 2001;85:4210

MAS as a Cytokine Storm

• Inflammatory infiltrate consists predominantly of macrophages (histiocytes) and T cells (mainly CD8+) • These cell produce large amounts of cytokines • T cell derived: IFN-γ, IL-2 • Monocyte/macrophage derived: IL-6, IL- 1, TNF-α, IL-18 • Henter, et al. Blood 1991;78:2918

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Liver Biopsy in MAS/SJIA

CD68+ macrophages

TNF-α IL-6

CD8+ T lymphocytes IFN-γ

Billiau, et al. Blood 2005;105:1648

SJIA / MAS Predominance of CD8+ T cells in Inflammatory Infiltrate

CD8+ T cells CD4+ T cells

Grom, et al. Nature Rev Rheumatol 2016

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Liver Biopsy in MAS

CD68+ macrophages

TNF-α IL-6

CD8+T Cells IFN-γ

Billiau, et al. Blood 2005;105:1648

Correlation with Ferritin Levels in Active SJIA with or without MAS

IFNg Rs=0.431 CXCL9 Rs=0.517 10,000 p=0.0077 1,000,000 p=0.0015 1,000 100,000

100 10,000

10 1,000 Full-blown MAS 1 100 10 100 1,000 10,000 100,000 10 100 1,000 10,000 100,000 CXCL10 Active sJIA 100,000 CXCL11 Rs=0.533 Rs=0.554 10,000 p=0.004 p=0.003 10,000

1,000 1,000

100 100 10 1,000 100,000 10 100 1,000 10,000 100,000 Ferritin (ng/ml) Bracaglia, et al. Ann Rheum Dis 2016

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Cytolytic Innate CD8+ T Cells immune IL-18 IL-18BP activation

Defective APC killing Cytokine IFNg Storm

Mf NK cell Hemophagocytosis IL-18 enhances IFNγ production? IL-18 TNF IL-1 IL-6 Proposed Mechanisms Leading to Cytokine Storm in MAS

MAS Diagnosis • In a patient with active rheumatologic condition • a fall in ESR and platelet count in combination with • persistently high CRP, and • increasing levels of serum D-dimers and decreasing fibrinogen should raise a suspicion of MAS

• Other supportive features • Cytopenias (overt cytopenias are seen only at late stages) • Liver dysfunction (may be seen in active sJIA) • Coagulopathy • May be seen in active sJIA • Elevated D-dimers in majority of patients Bloom, et al. J Rheumatol 1998;25:1620 • Hyperferritinemia (levels above 500 ng/dL are seen in >50% of patients with active systemic disease) • Hemophagocytic macrophages (or histiocytes) in BM biopsy • May not be apparent early in the course

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New Diagnostic Guidelines for MAS in SJIA

• A febrile patient with known or suspected SJIA is classified as having MAS if: - Ferritin > 684 ng/mL • And at least 2 of the following laboratory variables are present: - Platelets ≤ 181 x 106 L - Ast > 48 U/L - Triglycerides >156 mg/dL - Fibrinogen ≤ 360 mg/L

Ravelli, et al. A&R 2016

Emerging distinct clinical patterns of MAS

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Different MAS presentation/patterns in sJIA

MAS Classic sJIA sJIA MAS (Approx. 70%)

MAS MAS sJIA sJIA at sJIA onset (Approx. 25%)

MAS MAS MAS “relapsing” sJIA MAS (Approx. 5%)

Classic MAS

• The vast majority of patients have an active primary rheumatic disease prior to developing MAS, but • In the phase III clinical trials of the biologics inhibiting either IL-1 or IL- 6, MAS occurred in several patients despite an excellent control of the underlying systemic JIA. • Infectious triggers were identified in almost all of these cases • Clinical features could be modified by underlying biologics

Grom, et al. Arthritis&Rheumatol 2016;68:218 Schulert, et al. Arthritis Care &Res 2018:70:409

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Key lab features of MAS altered by biologics

Schulert, et al. Arthritis Care &Res 2018:70:409

Classic MAS

• The vast majority of patients have an active primary rheumatic disease prior to developing MAS, but • In the phase III clinical trials of the biologics inhibiting either IL-1 or IL-6, MAS occurred in several patients despite an excellent control of the underlying systemic JIA • Infectious triggers were identified in almost all of these cases • Clinical features could be modified by underlying biologics Grom, et al. Arthritis&Rheumatol 2016;68:218 Schulert, et al. Arthritis Care &Res 2018:70:409 • Utility of Ravelli’s MAS diagnostic guidelines may be limited Ravelli, et al. Arthritis&Rheumatol 2016;68:566

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Concept of subclinical MAS

• Evidence of subclinical MAS in a subgroup of systemic JIA patients with active systemic disease in about ~30% • Typical clinical pattern in subclinical MAS • Hepatosplenomegaly • Elevated Alt/Alt • Hyperferritinemia • Highly increased CRP • Relatively low platelet counts (low end of the normal range despite highly increased inflammatory markers ) • Fibrinogen tends to remain in the normal range despite highly increased CRP • Increased serum soluble IL2Rα chains • Expansion CD163+ macrophages in bone marrow (even in the absence of frank hemophagocytosis)

• Importance of early recognition of this pattern to prevent its’ evolution into life- threatening overt MAS

Bleesing, et al. Arthritis Rheum 2007;56:965 Behrens, et al. J Rheumatol 2007:34:1133

Bone marrow CD163+ macrophages in subclinical MAS

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Different MAS presentation/patterns in sJIA

MAS Classic sJIA sJIA MAS (Approx. 70%)

MAS MAS sJIA sJIA at sJIA onset (Approx. 25%)

MAS MAS MAS “relapsing” sJIA MAS (Approx. 5%)

MAS at presentation

• MAS at presentation may mask the underlying disease • Particularly challenging when presents with Kawasaki disease • Assessment of total IL-18 might help distinguish SJIA versus KD (↑↑↑ in SJIA) • Seems to be particularly prevalent in SLE • associated with a higher risk of death.

Borgia, et al. Arthritis&Rheumatol 2018;70:616

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Different MAS presentation/patterns in sJIA

MAS Classic sJIA sJIA MAS (Approx. 70%)

MAS MAS sJIA sJIA at sJIA onset (Approx. 25%)

MAS MAS MAS “relapsing” sJIA MAS (Approx. 5%)

Relapsing MAS

• These patients appear at risk for SJIA- associated lung disease

• A proportion of these patients have predominantly liver involvement

Schulert, et al. Arthritis&Rheumatol 2019 Saper, et al. Ann Rheum Dis 2019;78:1722 Canna, et al. Pediatr Rheumatol Online J 2020;18(S1):53.

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MAS with predominantly liver involvement

• Persistently elevated liver enzymes with lab features of subclinical MAS (but do not meet full criteria for MAS) • Highly characteristic findings in liver biopsy • Sinusoidal inflammatory infiltrate that consists both of increased number of T lymphocytes and CD163+ macrophages • Highly activated Kupffer cells with some of them exhibiting hemophagocytic activity • Amongst T lymphocutes, marked predominance of CD8+ T cells of CD4+ • Immunostaining for cytokines identifies CD8+ T cells as the main producers of large amounts of IFN-γ • May have normal BM biopsy Billiau, et al. Blood 2005;105:1648

Liver Biopsy in MAS/SJIA

CD68+ macrophages

TNF-α IL-6

CD8+ T lymphocytes IFN-γ

Billiau, et al. Blood 2005;105:1648

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• Regardless of the clinical pattern of MAS, IFN-γ and IL-18 are emerging as pivotal cytokines

Bracaglia, et al. Ann Rheum Dis 2016 Weiss et al, Blood 2018;131;1441 Canna, et al. Pediatr Rheumatol Online J. 2020;18(Suppl 1):53.

Treatment of MAS

• No approved medications • No randomized clinical trials • Common treatment approaches are based on small series reported in the literature

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MAS treatment

• High dose steroids • Methylprednisolone IV pulses (30 mg/kg daily for 3-5 days) • then IV 2-3 mg/kg in 2-3 divided doses • CyA (2-5 mg/kg in two divided doses PO or IV) • Rituximab (anti-CD20 mAbs) (in EBV–induced MAS) • Low dose etoposide? • Biologics targeting cytokines? • Tocilizumab and canakinumab do not provide protection against MAS • Anakinra is effective in many cases (role for IL1α?)

Cytolytic Innate CD8+ T Cells immune IL-18 IL-18BP activation

Defective APC killing Cytokine IFNg Storm

Mf NK cell Hemophagocytosis IL-18 enhances IFNγ production? IL-18 TNF IL-1 IL-6

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Targeting IFN-γ in MAS

• A pilot open-label single arm international study (NCT03311854) of Emapalumab, an interferon gamma (IFNg)-blocking monoclonal antibody, in patients with MAS complicating SJIA • SJIA patients with MAS (defined according to the 2016 ACR/EULAR classification criteria) with inadequate response to high-dose IV glucocorticoids • Emapalumab initial dose was 6 mg/kg then at 3 mg/kg, twice weekly for a total of 4 weeks or less upon achievement of complete response

De Benedetti, et al., EULAR 2019 Abstract OP0204

Study Overview and Dosing Regimen

EMAPALUMAB

6 mg/kg 3 mg/kg1,2

every 3 days twice a week

End of Study 0 3 15 28 35 42 49 56

SCREENING TREATMENT PERIOD EVALUATION PERIOD

Glucocorticoid dose can be increased or decreased

Short-term follow-up after last emapalumab dose Efficacy/safety visits to be performed weekly

1 Treatment may be shortened upon achievement of complete response 2 Emapalumab32 dose may be increased or treatment prolonged in the event of very high IFNg production

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Main Inclusion/Exclusion Criteria • Confirmed, or high presumption of, sJIA 1 • Diagnosis of active MAS confirmed by the treating rheumatologist ascertaining the fulfillment of the 2016 ACR/EULAR classification criteria for MAS 2 • Inadequate response to high dose i.v. glucocorticoid administered for at least 3 days as per local standard of care 3 • Absence of suspected or confirmed primary HLH or HLH consequent to a neoplastic disease • No evidence of active infections by mycobacteria (typical and atypical), Histoplasma Capsulatum, Shigella, Salmonella, Campylobacter and Leishmania • No treatment with tocilizumab, canakinumab or TNF inhibitors within 5 times of their defined half-life

1 ILAR criteria (confirmed) or presumptive (CARRA criteria) for sJIA 2 Febrile patient with sJIA with ferritin > 684 ng/mL, and any 2 of the followings: platelet count  181 x109/L, AST levels > 48 U/L, triglycerides > 156 mg/d, fibrinogen levels ≤ 360 mg/dL 3 In case of rapid worsening of the patient’s condition and/or lab parameters, inclusion may occur within less than 3 days from starting high dose i.v. glucocorticoids

Rapid neutralization of IFN-γ as demonstrated by decrease in serum CXCL9 levels

100.000

10.000

/ml) pg 1.000

th CXCL9 CXCL9 ( 95 percentile in healthy subjects 100

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Response to emapalumab Efficacy primary outcome: Complete Response at week 8 Resolution of clinical signs and symptoms as assessed by Investigator AND Normalization of laboratory parameters relevant to MAS, as follows: . WBC and platelet count above lower limit of normal . LDH below 1.5 upper limit of . ALT/AST below 1.5 ULN . Fibrinogen > 100 mg/dL . Ferritin levels decreased by at least 80% from values at screening or baseline (whichever is higher) or below 2000 ng/ml, whichever is lower.

6/12 patients achieved complete response at week 4 12/12 patients achieved complete response at week 8

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MAS Laboratory Abnormalities Over Time

9 Ferritin (mg/L) 500 Platelets (x10 /L) 25000 emapalumab emapalumab 400 Median values 20000 300 15000

10000 200

5000 100

0 0 0 7 14 21 28 35 42 49 56 0 7 14 21 28 35 42 49 56

D-Dimer (mg/L) LDH (IU/L) AST (IU/L) 150 2500 12000 emapalumab emapalumab emapalumab 125 10000 2000 100 8000 1500 75 6000 1000 4000 50

2000 500 25

0 0 0 0 7 14 21 28 35 42 49 56 0 7 14 21 28 35 42 49 56 0 7 14 21 28 35 42 49 56 36 DAY DAY DAY

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Targeting Cytokines in MAS Summary • Strategies aimed at blocking TNF, IL-6 and IL-1β are not effective • IL1α? • anakinra is beneficial in some MAS patients, but higher doses might be necessary • IL-18 - need more data • Phase I-II trail under development • IFN-γ – an attractive therapeutic target • Preliminary results of anti-IFNγ antibodies are promising

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