Innovative Approaches in Treating Inflammatory Myopathies: From Empirical to Targeted Therapies

From Empirical to Targeted Therapies

Rheumatology · Seminar week 42 · released October 19, 2026 · includes a discussion video

The management of inflammatory myopathies is evolving, with a shift towards targeted therapies. The VALOR trial discusses the use of reposainib, a JAK1/TYK2 inhibitor, in…

Learning Objectives

• Classify idiopathic inflammatory myopathies by phenotype, autoantibody, pathology, and threatened organ rather than relying on the historical label “polymyositis.”
• Distinguish active inflammatory disease from mimics, treatment toxicity, deconditioning, and irreversible muscle damage.
• Construct an induction, steroid-sparing, monitoring, rehabilitation, and prophylaxis plan for common IIM phenotypes.
• Explain how interferon–JAK–STAT signaling, pathogenic IgG, and lymphocyte biology support targeted treatment strategies.
• Critically appraise the design, efficacy, safety, and limits of the phase 3 VALOR trial of brepocitinib.
• Integrate emerging FcRn, interferon-directed, and cellular therapies without treating preliminary evidence as established care.
• Apply a phenotype-first treatment algorithm to a patient with dermatomyositis and incomplete response to conventional therapy.

Introduction to Idiopathic Inflammatory Myopathies (IIM)

%%FIG0%% Framework: “Myositis” is a syndromic starting point, not a final diagnosis. Idiopathic inflammatory myopathies are uncommon systemic immune-mediated diseases in which muscle, skin, lung, joints, swallowing, heart, and cancer risk may matter in different proportions. The clinically useful question is not simply “Does this patient have myositis?” but “Which biologic phenotype is present, which organ is in danger, and how much of the disability is still reversible?” The 2017 EULAR/ACR criteria provide a probability-based research classification—probable IIM begins at 55% probability—but they do not replace bedside diagnosis and predate several modern antibody-defined entities (PMID: 29079590).

Dermatomyositis (DM) is defined by its characteristic cutaneous biology, with or without overt myopathy. Gottron papules or sign and a heliotrope eruption are especially discriminating; shawl, V-sign, holster erythema, scalp inflammation, periungual capillary change, and pruritus add support. Muscle disease is usually subacute, symmetric, and proximal, involving hip and shoulder girdles and neck flexors. Yet clinically amyopathic DM may have active skin or lung disease with normal strength and creatine kinase (CK). Pathology often shows perifascicular atrophy and perivascular or perimysial inflammation; sarcoplasmic myxovirus-resistance protein A reflects type I interferon activation. Complement-mediated microangiopathy, interferon-stimulated keratinocytes and myofibers, plasmacytoid dendritic cells, and adaptive immunity all contribute.

Antisynthetase syndrome is a multisystem phenotype associated with antibodies to aminoacyl-tRNA synthetases—most commonly Jo-1, but also PL-7, PL-12, EJ, OJ, and others. Interstitial lung disease (ILD), inflammatory myopathy, nonerosive arthritis, mechanic’s hands, Raynaud phenomenon, and fever may appear sequentially; absence of the “complete triad” does not exclude it. Immune-mediated necrotizing myopathy (IMNM) causes abrupt or subacute severe proximal weakness, often with CK in the thousands, and biopsy showing necrosis and regeneration with relatively sparse lymphocytic inflammation. Anti-HMGCR disease may follow statin exposure but persists after statin withdrawal and also occurs in statin-naïve patients; anti-SRP disease is often severe, dysphagic, and treatment-resistant. Seronegative IMNM remains a diagnosis requiring careful exclusion of toxic, inherited, and cancer-associated disease.

Inclusion body myositis (IBM) is both inflammatory and degenerative. It typically evolves over years after age 40–50, with asymmetric quadriceps and deep finger-flexor weakness, falls, and dysphagia. Endomysial CD8-positive inflammation, invasion of non-necrotic fibers, rimmed vacuoles, protein aggregates, and mitochondrial abnormalities may coexist. Anti-cN1A is supportive but neither sensitive nor specific. No pharmacologic therapy has shown durable disease modification; repeated prednisone escalation usually adds harm (PMID: 39843353). “True” polymyositis is now rare: it requires a compatible endomysial T-cell myopathy after excluding DM without obvious rash, antisynthetase syndrome, IMNM, IBM, overlap myositis, drug toxicity, infection, endocrine disease, and inherited myopathy.

Teaching Point: Autoantibodies enrich probability and forecast organs; they do not make the diagnosis alone. Anti-MDA5 flags amyopathic or ulcerative DM and rapidly progressive ILD; anti-TIF1γ strongly raises adult malignancy concern; anti-Mi-2 favors classic rash and prominent, often treatment-responsive myositis; anti-NXP2 associates with edema, dysphagia, severe weakness, and calcinosis; anti-SAE disease may begin in skin before muscle. Weak or multiple positives on commercial line blots can be false and should be reconciled with phenotype or confirmed when consequential (PMID: 32699830).

MUST ACT: At the first assessment, actively search for oxygen desaturation, rapidly progressive dyspnea, aspiration, respiratory-muscle weakness, and myocarditis. At-risk patients require pulmonary function tests and high-resolution CT—not a reassuring chest radiograph alone (PMID: 38973729). For suspected cardiac involvement, obtain ECG, echocardiography as appropriate, and cardiac troponin I; troponin T can arise from regenerating skeletal muscle. Adult-onset IIM also triggers risk-stratified malignancy screening, particularly within three years of onset; DM, anti-TIF1γ, age over 40, refractory activity, dysphagia, and cutaneous necrosis or ulceration increase risk (IMACS guideline, PMID: 37945774).

Diagnosis integrates tempo and weakness pattern, complete skin examination, CK plus aldolase, AST/ALT and LDH, blood count and metabolic testing, antibody phenotype, MRI, electromyography, and selective biopsy. MRI T2/STIR edema identifies active regions but is not specific; T1 fatty replacement signals damage less likely to respond. Biopsy a moderately weak, MRI-active muscle, avoiding end-stage tissue and a recently needled site. Important mimics include glucocorticoid myopathy, self-limited statin toxicity, thyroid or Cushing disease, electrolyte disorders, infection, colchicine or hydroxychloroquine vacuolar myopathy, muscular dystrophy, metabolic myopathy, neuropathy, myasthenia, and deconditioning.

Nuance: CK is a biomarker, not a verdict. It may be normal in active DM, MDA5 disease, or lung-predominant antisynthetase syndrome, and it may fall before strength returns. Conversely, worsening weakness with normal CK, absent MRI edema, and prolonged glucocorticoid exposure should raise steroid myopathy or accumulated damage rather than trigger an automatic dose increase.

Audience Poll: Which finding most changes your first-hour plan: CK 12,000 U/L, anti-MDA5 positivity with new hypoxemia, severe dysphagia with nasal speech, or a TIF1γ-positive DM phenotype with weight loss?

Traditional Management Strategies for Myositis

%%FIG1%% Framework: Conventional care is not one ladder. It is a coordinated plan with five simultaneous lanes: suppress active inflammation, protect threatened organs, introduce a glucocorticoid-sparing drug early, prevent treatment toxicity, and restore function. Phenotype determines the order. A patient with mild muscle and cutaneous disease can be managed deliberately; anti-MDA5 rapidly progressive ILD, respiratory weakness, myocarditis, or aspiration is an emergency requiring multidisciplinary combination therapy.

For active adult DM, antisynthetase myositis, overlap myositis, or IMNM, prednisone or prednisolone 0.5–1 mg/kg/day—commonly 40–60 mg/day—is a typical induction regimen. Severe dysphagia, profound weakness, respiratory or cardiac involvement, or rapidly progressive ILD often prompts intravenous methylprednisolone 500–1,000 mg daily for three days, followed by oral therapy. Start a steroid-sparing agent at or near diagnosis rather than waiting for toxicity. Once objective strength, function, skin, lung, or swallowing measures improve—often after four to six weeks—begin an individualized taper. There is no evidence-based universal taper, and a falling CK alone is insufficient permission to taper or a reason not to taper (BSR guideline, PMID: 35355064).

Common regimens include methotrexate 15 mg once weekly, titrated to 20–25 mg with folate; azathioprine approximately 1.5–3 mg/kg/day after TPMT/NUDT15 assessment; and mycophenolate mofetil 500 mg twice daily, titrated toward 1–1.5 g twice daily. Methotrexate treats muscle, joint, and skin disease but is teratogenic and can complicate pulmonary-toxicity attribution. Mycophenolate is often favored when skin disease or ILD dominates but causes gastrointestinal toxicity, cytopenia, infection, and fetal harm. Tacrolimus, often begun around 1–2 mg twice daily and titrated to a center-specific trough, is valuable in IIM-ILD but requires renal, blood-pressure, electrolyte, glucose, neurologic, and interaction monitoring.

Decision Point: Choose the steroid-sparing drug by the organ you most need to save. For stable muscle-predominant disease, methotrexate or azathioprine may be reasonable. For clinically important ILD, mycophenolate, tacrolimus or cyclosporine, rituximab, or cyclophosphamide may be preferred. The 2023 ACR/CHEST guideline supports upfront combination treatment for rapidly progressive IIM-ILD and conditionally favors triple therapy when MDA5 disease is suspected or confirmed rather than glucocorticoid monotherapy (PMID: 38973731). Cyclophosphamide is reserved for selected organ-threatening disease because marrow, bladder, gonadal, infectious, and malignancy toxicities accumulate.

Intravenous immune globulin (IVIG) is neither merely a last resort nor benign. A practical adult DM regimen is 2 g/kg per cycle divided over two to five days every four weeks. In ProDERM, 79% of IVIG-treated participants versus 44% receiving placebo achieved at least minimal improvement at week 16; CK itself did not distinguish groups (PMID: 36198179). IVIG can be attractive when rapid control is needed, dysphagia is prominent, infection makes additional immunosuppression undesirable, severe skin disease persists, or anti-HMGCR IMNM is present. Assess renal function, volume and hyperviscosity risk, hydrate appropriately, slow the infusion, and recognize headache, aseptic meningitis, hemolysis, renal injury, and thrombosis; ProDERM recorded six treatment-related thromboembolic events.

Rituximab is frequently used off-label for refractory, autoantibody-positive disease, antisynthetase syndrome, or ILD. Common regimens are 1 g IV on days 1 and 15 or 375 mg/m² weekly for four doses. The RIM trial did not meet its randomized timing endpoint—median time to improvement was about 20 weeks in both early and delayed groups—although 83% improved after all ultimately received rituximab (PMID: 23124935). That supports selective use, not a claim of a positive placebo-controlled trial. Screen hepatitis B, update vaccines before B-cell depletion, measure immunoglobulins, and monitor infusion reactions, late neutropenia, hypogammaglobulinemia, and infection.

Cutaneous care requires photoprotection, topical corticosteroids or calcineurin inhibitors, and hydroxychloroquine 200–400 mg/day, not exceeding 5 mg/kg/day actual body weight or 400 mg/day, with retinal screening. Hydroxychloroquine treats skin, not myositis, and drug eruptions are relatively frequent in DM. Refractory skin disease may need methotrexate, mycophenolate, or IVIG. In IBM, pivot from chronic immunosuppression to exercise, rehabilitation, falls prevention, assistive devices, nutrition, and serial swallowing assessment.

MUST ACT: Every prescription needs a toxicity bundle: vaccination before major immunosuppression when feasible; CBC, renal and liver monitoring; glucose and blood-pressure management; calcium/vitamin D and fracture-risk treatment; pregnancy and contraception counseling; and individualized Pneumocystis prophylaxis, particularly with prednisone at least 20 mg/day for four weeks plus another immunosuppressant. Evaluate aspiration early and involve speech-language pathology.

Nuance: A patient labeled “refractory” may have an incorrect subtype, nonadherence, occult infection or cancer, steroid myopathy, critical-illness neuropathy, deconditioning, or T1 fatty replacement. Before adding a third immunosuppressant, repeat objective strength and function, review MRI activity, and ask whether the proposed target is active inflammation or irreversible damage.

Teaching Point: Supervised aerobic and resistance exercise is a disease-management intervention, not an optional afterthought. When individualized for activity and cardiopulmonary status, it improves capacity and function without routinely worsening inflammation.

Audience Poll: After six weeks of prednisone and mycophenolate, CK normalizes but chair-rise time worsens. Do you escalate immunosuppression, obtain objective reassessment for damage or steroid myopathy, switch agents immediately, or wait for CK relapse?

Emergence of Targeted Therapies

%%FIG2%% MUST ACT: Correct the nomenclature before interpreting the figure: VALOR studied brepocitinib (PF-06700841/PVT-2201), not “reposainib.” No recognized drug or myositis trial under the name reposainib can be substantiated. The required image tag above retains the legacy alt text, but the molecule discussed throughout this seminar is brepocitinib. This is clinically important because an incorrect nonproprietary name can propagate into consent, prescribing, and literature searches.

Framework: Targeted therapy begins by matching a pathway to a phenotype, then proving that pathway inhibition changes outcomes that matter. In DM, a strong type I interferon signature appears in blood, skin, and muscle. TYK2 and JAK1 transmit signals from type I and II interferons and other cytokines; B cells and IgG autoantibodies contribute across DM, antisynthetase syndrome, and IMNM; T-cell cytotoxicity is particularly relevant in IBM and some overlap phenotypes. These observations create plausible targets, but biologic plausibility is not comparative effectiveness. “Targeted” does not mean uniquely specific, safer, or superior to conventional therapy.

Brepocitinib is an oral selective TYK2/JAK1 inhibitor that attenuates signaling downstream of type I interferons, interferon-γ, IL-12, IL-23, and portions of IL-6 biology (mechanistic review, PMID: 39008325). That breadth may be advantageous in multisystem DM but also means the drug is not an interferon-only switch. Before VALOR, small studies of other JAK inhibitors supported target plausibility. In the 12-week, open-label STIR pilot, ten patients with refractory, predominantly cutaneous DM received tofacitinib XR 11 mg daily; all met an improvement definition and mean CDASI activity fell substantially, but the cohort was tiny, uncontrolled, and had little active myositis by CK (PMID: 33258553). Tofacitinib, baricitinib, and upadacitinib therefore remain off-label for DM rather than interchangeable substitutes for brepocitinib evidence.

Direct interferon blockade offers a narrower experiment. Dazukibart, a humanized monoclonal antibody neutralizing interferon-β, was studied in a 75-participant phase 2 trial. In pooled skin-predominant cohorts, 150 mg or 600 mg IV every four weeks through week 8 produced large placebo-adjusted improvements in CDASI activity at week 12, supporting target engagement and phase 3 study; it remains investigational, and the modest sample and short controlled period limit safety and organ-specific conclusions (PMID: 39798982). Anifrolumab, which blocks IFNAR1 and is approved for lupus, is also under study in IIM, but no efficacy result should yet drive routine myositis care.

Depleting B cells with rituximab is biologically targeted, yet RIM illustrates why mechanism cannot rescue a difficult trial design. Abatacept targets CD80/86-mediated T-cell costimulation. In a 148-patient phase 3 IIM trial, abatacept 125 mg subcutaneously weekly plus standard care yielded improvement in 56.0% versus 42.5% with placebo plus standard care at week 24, but the primary comparison was not significant; a non-DM subgroup signal remains hypothesis-generating (PMID: 39609094). These data argue for better subtype selection, not for declaring all biologics ineffective.

Teaching Point: IVIG is currently the strongest randomized and regulatory precedent for adult DM, but it is broad immunomodulation rather than a single-pathway drug. ProDERM showed that a clinically meaningful composite can improve while CK does not. Modern development therefore uses multidomain outcomes: the ACR/EULAR Total Improvement Score (TIS) combines physician and patient global assessments, MMT-8, physical function, the most abnormal muscle enzyme, and extramuscular disease activity. Adult thresholds of at least 20, 40, and 60 indicate minimal, moderate, and major improvement (PMID: 28385805).

Decision Point: Before considering a JAK/TYK2 strategy, define the intended target—skin, muscle, steroid dependence, arthritis, or lung—and establish baseline measures. Review tuberculosis and hepatitis risk, vaccination including recombinant zoster, CBC, liver tests, lipids, pregnancy, infection history, malignancy context, smoking, cardiovascular risk, and thrombosis history. These are anticipated JAK-class precautions; until an approved brepocitinib label exists, they are not a substitute for trial eligibility or regulatory guidance.

Nuance: Do not infer efficacy across phenotypes. VALOR enrolled active, previously treated adult DM with muscle and skin criteria; it did not establish treatment for clinically amyopathic DM, MDA5 rapidly progressive ILD, antisynthetase syndrome, IMNM, IBM, cancer-associated DM, or monotherapy. Nor did it compare brepocitinib head-to-head with IVIG, rituximab, mycophenolate, or tacrolimus.

Audience Poll: What would persuade you to choose a pathway-specific therapy: a higher mean TIS, faster skin response, successful steroid withdrawal, a predictive biomarker, or direct superiority over your current steroid-sparing regimen?

Detailed Overview of the VALOR Trial

%%FIG3%% MUST ACT: Read VALOR as a positive phase 3 trial of brepocitinib 30 mg once daily added to continued standard therapy with protocolized glucocorticoid taper, not as a trial of “reposainib,” not as monotherapy, and not as an active comparison against conventional treatment. The peer-reviewed report is Vleugels and colleagues, New England Journal of Medicine 2026 (PMID: 41910335; NCT05437263).

VALOR was a global, multicenter, randomized, double-blind, placebo-controlled 52-week study conducted at approximately 90 sites. It randomized 241 adults 1:1:1 to brepocitinib 30 mg daily (n=81), brepocitinib 15 mg daily (n=81), or placebo (n=79). Participants had probable or definite DM, active cutaneous disease, active muscle disease, and disease that had been refractory or intolerant to previous therapy. Stable background oral glucocorticoids, immunosuppressants, and antimalarials were permitted. Oral glucocorticoid taper toward no more than 5 mg/day was mandated between weeks 12 and 36, with further reduction encouraged. That taper is not a nuisance detail: it stress-tested whether disease control persisted as a potent confounder and source of toxicity was withdrawn.

Framework: The primary endpoint was mean TIS at week 52, scored from 0 to 100, not a binary strength endpoint. The weighted TIS incorporates change in physician global activity, patient global activity, MMT-8, Health Assessment Questionnaire function, the most abnormal muscle enzyme, and extramuscular disease activity. A mean difference can reflect modest gains across several domains or a major gain in a subset; therefore, examine categorical response, skin, strength, function, steroid exposure, rescue therapy, and safety alongside the primary number.

At week 52, mean TIS was 46.5 with 30 mg, 37.5 with 15 mg, and 31.2 with placebo. The adjusted 30-mg–placebo difference was 15.3 points (95% CI 6.7–24.0; P<0.001). The 15-mg–placebo difference was 6.3 points (95% CI −2.4 to 14.9) and was not significant. The dose-response matters: VALOR supports 30 mg, not a generic conclusion that any TYK2/JAK1 inhibition or lower exposure is sufficient.

The 30-mg arm also met all nine multiplicity-controlled key secondary endpoints. Moderate improvement, TIS at least 40, occurred in 67.9% versus 44.3% with placebo; major improvement, TIS at least 60, occurred in 46.1% versus 26.4%. Median time to sustained TIS at least 40 was 85 versus 168 days. CDASI activity improved by 11.7 versus 7.0 points at week 52, with separation already present at week 4. Functional disability improved: HAQ-DI changed by −0.337 versus −0.042. Among participants taking glucocorticoids at baseline, 62% versus 34% reached no more than 2.5 mg/day, and 42% versus 23% discontinued glucocorticoids. These results are clinically coherent across disease activity, skin, function, timing, and steroid sparing rather than resting on one laboratory marker.

Teaching Point: The placebo group achieved a mean TIS of 31.2—within minimal-to-moderate improvement—because background therapy continued, glucocorticoid exposure changed, composite components contain subjective elements, and trial participation itself modifies care. The relevant estimate is the between-group difference with its confidence interval, not the active-arm score in isolation. Completion was higher and rescue therapy lower with 30 mg than placebo, but handling of missing data, rescue, and taper remains essential when translating efficacy.

Safety prevents an uncomplicated “practice-changing” slogan. Serious infections occurred in 10% with 30 mg, 2% with 15 mg, and 1% with placebo; no deaths occurred. Overall serious adverse events were numerically 16%, 9%, and 13%, respectively. Cardiovascular, thromboembolic, and malignancy events were not more frequent with 30 mg during the one-year trial, but event counts were too small and follow-up too short to infer protection or erase JAK-class concerns.

Nuance: Generalizability is narrower than the label “dermatomyositis.” Key eligibility requirements selected patients with measurable active skin and muscle disease; exclusions included important end-stage organ damage, recent active cancer or cancer-associated disease, many overlap phenotypes, active infection, and specified cardiovascular, thrombotic, or zoster risks. VALOR did not establish a benefit in rapidly progressive ILD or prove prevention of malignancy, irreversible damage, or long-term disability.

Decision Point: As of July 14, 2026, brepocitinib is investigational in the United States. The FDA has accepted its NDA with Priority Review and a target action date in the third quarter of 2026, but a successful trial and accepted application are not approval. Do not prescribe an anticipated label. Pending regulatory action, access should occur through a clinical trial or another lawful investigational pathway; after any approval, use the final indication, dose, contraindications, warnings, and monitoring requirements.

Audience Poll: Does a 15.3-point mean TIS advantage plus steroid sparing outweigh a 10% serious-infection rate for your refractory patient—and which patient-level factors would reverse that judgment?

Future Directions in Myositis Treatment

%%FIG4%% Framework: The next advance is unlikely to be one universal “myositis drug.” It will be a sequence: define phenotype and dominant organ, quantify active rather than damaged tissue, select a pathway, measure early target engagement, and stop or switch when the predicted response does not occur. Future trials must stratify DM, antisynthetase syndrome, IMNM, overlap disease, and IBM rather than dilute divergent mechanisms inside one diagnostic basket.

FcRn inhibition tests whether reducing circulating IgG can improve autoantibody-associated IIM without directly eliminating B cells. The neonatal Fc receptor normally rescues IgG from lysosomal degradation; blocking it lowers total and potentially pathogenic IgG. In the 24-week phase 2 portion of ALKIVIA, preliminary conference data in 89 adults across DM, IMNM, antisynthetase syndrome, and selected polymyositis reported a mean TIS of 50.45 with weekly subcutaneous efgartigimod-PH20 versus 35.65 with placebo, with moderate improvement in 78.7% versus 47.6%. The seamless phase 3 program is ongoing (NCT05523167). These are encouraging phase 2 conference-abstract data, not a completed peer-reviewed phase 3 dataset or an approved regimen. FcRn blockade may lower protective IgG as well as autoantibody, so infection, vaccination timing, baseline IgG, and phenotype-specific benefit remain central.

Interferon-directed therapy may permit cleaner biologic matching. The phase 2 dazukibart trial showed rapid, substantial improvement in skin-predominant DM and supports the hypothesis that interferon-β is a driver, not merely a marker (PMID: 39798982). Phase 3 studies must now show durability, muscle and systemic benefit, steroid sparing, and acceptable safety. Interferon signatures, MxA staining, or serum chemokines are attractive enrichment biomarkers, but none should be used clinically to promise response until prospectively validated.

Teaching Point: CAR-T therapy is an attempt at immune-system reconstitution, not a stronger rituximab infusion. Autologous CD19-directed CAR T cells can deeply deplete B-lineage cells after leukapheresis, bespoke manufacturing, and fludarabine/cyclophosphamide lymphodepletion. In a 2024 autoimmune series, all three IIM participants achieved major responses and stopped immunosuppression (PMID: 38381673). An earlier severe antisynthetase case also improved but received mycophenolate after CAR-T, preventing attribution to CAR-T alone (PMID: 37367976); the first RESET-Myositis IMNM participant is reported under PMID: 39245937. These signals justify trials, not routine referral as established therapy.

The risks and logistics are qualitatively different from oral immunosuppression: cytokine-release syndrome, immune-effector-cell neurotoxicity, prolonged cytopenias, infection, hypogammaglobulinemia, impaired vaccine responses, hospitalization, fertility considerations, secondary malignancy surveillance, manufacturing delay, and high cost. Relapse after CD19 CAR-T has occurred, including a reported Jo-1 antisynthetase case later treated with BCMA-directed CAR-T, reminding us that plasma cells or non-B-cell pathways may sustain disease. Off-the-shelf CAR-NK, bispecific immune engagers, and in-vivo CAR engineering may eventually simplify access, but each introduces new control and safety problems.

Nuance: A positive composite endpoint can conceal organ mismatch. A therapy that improves skin and patient global scores may not rescue falling FVC; a drug that normalizes CK may not reverse fatty replacement; an IBM therapy must alter slope of function over years, not transiently suppress enzymes. Future trials need parallel CDASI, MMT and performance measures, FVC/DLCO and oxygen outcomes, swallowing endpoints, digital mobility, patient-reported fatigue and pain, cumulative glucocorticoid dose, damage indices, and long-term safety.

Better trial architecture is equally innovative. Rare-disease networks can use adaptive or platform designs, centralized antibody confirmation, MRI and digital biomarkers, organ-specific cohorts, and standardized rescue rules. Pragmatic sequencing studies should ask whether targeted therapy belongs at diagnosis, after one conventional agent, or only after refractory disease; whether combination treatment is additive or simply more toxic; and when therapy can be withdrawn. Head-to-head and steroid-withdrawal designs are especially important because uncontrolled improvement is difficult to interpret in a relapsing disease.

MUST ACT: Do not read a pipeline chart as a treatment menu. Confirm regulatory status, trial phase, studied phenotype, comparator, endpoint, dose, and safety denominator before counseling a patient. “FDA-approved in another autoimmune disease,” “met a biomarker endpoint,” and “reported at a congress” are not equivalent to demonstrated clinical benefit in IIM.

Decision Point: The practical future is biomarker-informed but outcome-governed. Use antibodies and interferon biology to select a plausible therapy, then continue only if prespecified patient-relevant domains improve while glucocorticoid burden and toxicity fall.

Audience Poll: Which development would most improve care: a validated response biomarker, an oral steroid-replacing agent, an ILD-specific platform trial, durable drug-free remission after cellular therapy, or a treatment that changes IBM functional decline?

Case Discussions and Clinical Application

%%FIG5%% Teaching Point: The safest personalized plan is phenotype-first and measurement-first. “Refractory myositis” should never be accepted without confirming the diagnosis, identifying the active domain, quantifying damage, and auditing what adequate treatment actually occurred.

A 46-year-old woman presents with eight weeks of difficulty rising from a chair, washing her hair, and swallowing dry food. She has a pruritic heliotrope eruption, Gottron papules, periungual capillary dropout, and shawl erythema. Hip flexors and shoulder abductors are 4−/5; deep finger flexors are preserved. CK is 2,480 U/L, aldolase is elevated, and AST/ALT are 118/96 U/L with normal γ-glutamyl transferase, favoring muscle rather than liver release. ECG and troponin I are normal. Pulmonary function, ambulatory saturation, and high-resolution CT show no ILD. MRI shows edema without extensive T1 fatty replacement. Anti-Mi-2 is strongly positive; MDA5, TIF1γ, NXP2, antisynthetase, HMGCR, and SRP antibodies are negative.

The leading diagnosis is classic DM. IBM is unlikely given the short tempo and preserved finger flexors; IMNM can explain high CK but not the pathognomonic rash. Steroid myopathy cannot precede steroid exposure and would not cause CK elevation or MRI edema. Thyroid disease, infection, drug toxicity, inherited myopathy, and immune-checkpoint-inhibitor myositis still require exclusion. With a coherent phenotype, muscle biopsy is reserved for meaningful uncertainty rather than performed reflexively.

MUST ACT: Complete threat assessment before celebrating the antibody result. Obtain a formal swallowing evaluation because dysphagia predicts aspiration and malignancy risk. Review pulmonary, cardiac, rheumatic, and constitutional symptoms. Continue routine age-appropriate cancer screening and apply IMACS risk stratification. Adult DM plus onset after age 40 places her in the IIM-relative high-risk category: perform basic and enhanced screening at diagnosis and basic screening annually for three years if initial evaluation is negative (PMID: 37945774).

She weighs 72 kg and has no aspiration, pregnancy plan, liver disease, or major infection. A reasonable induction is prednisone 60 mg daily with methotrexate 15 mg weekly plus folate, titrating toward 20–25 mg. Mycophenolate is an alternative when skin or lung concerns dominate. Add topical therapy, photoprotection, graded rehabilitation, fracture prevention, vaccination review, metabolic monitoring, and Pneumocystis prophylaxis while high-dose prednisone is combined with another immunosuppressant. Prespecify success: better MMT-8 and chair-rise, safer swallowing, lower CDASI activity, recovered daily function, and prednisone reduction—not CK normalization alone.

At week six, CK has fallen to 620 U/L, strength and swallowing improve, and prednisone taper begins. At month four, taper below 20 mg triggers renewed rash, slower chair-rise, and MRI edema despite methotrexate 25 mg weekly. After reassessing adherence, infection, malignancy, and steroid myopathy, the concordant findings support active disease. IVIG 2 g/kg over three days every four weeks is added after thrombosis and renal-risk assessment. She improves to prednisone 7.5 mg but retains moderate skin activity.

Decision Point: The next choice is not an automatic “switch to brepocitinib.” Established options include optimizing or changing the conventional agent, continuing IVIG if benefit is meaningful, and selectively considering rituximab based on phenotype and risks. Enrollment in a targeted-therapy trial may be attractive. VALOR closely resembles her active, previously treated muscle-and-skin phenotype and suggests that brepocitinib 30 mg can improve multidomain activity and facilitate steroid withdrawal, but as of July 14, 2026 it remains under FDA review. If approval occurs, the final label and her infection, zoster, cardiovascular, thrombotic, malignancy, pregnancy, laboratory, and drug-interaction risks must govern use.

Audience Poll: For this patient, which outcome would justify changing therapy: inability to taper prednisone below 10 mg, persistent CDASI activity, plateaued strength, recurrent dysphagia, or any one of these after confirming objective inflammation?

Now alter one fact: she develops new hypoxemia and rapidly progressive ground-glass opacities with anti-MDA5 positivity. The center of gravity shifts from outpatient steroid sparing to an ILD emergency. Admit, exclude infection in parallel, involve rheumatology, pulmonology, intensive care and transplant expertise early, and use prompt upfront combination therapy rather than waiting for serial single-agent failures. VALOR cannot be extrapolated to promise control of this phenotype. Alter a different fact—she is 72 with three years of asymmetric quadriceps and finger-flexor weakness, dysphagia, modest CK elevation, and rimmed vacuoles—and the plan pivots to IBM rehabilitation and swallowing protection, not escalating immunosuppression.

Nuance: Precision care sometimes means choosing less immune therapy. The same symptom—difficulty rising from a chair—can represent active DM, anti-SRP IMNM, IBM, glucocorticoid myopathy, neuropathy, osteoarthritis pain, or irreversible fatty replacement. A treatment algorithm is safe only when it contains an off-ramp for diagnostic revision.

Framework: At every visit, state four things explicitly: the working subtype; the active and damaged domains; the organ or toxicity most likely to cause near-term harm; and the measurable threshold for continuing, tapering, switching, or stopping therapy. That discipline converts “empirical versus targeted” from a marketing contrast into accountable clinical decision-making.

Tonight on Shift

• Recognize: Treat new hypoxemia, rapidly progressive ILD, aspiration, respiratory weakness, or suspected myocarditis as an organ-threatening IIM presentation requiring urgent multidisciplinary care.
• Phenotype: Separate DM, antisynthetase syndrome, IMNM, IBM, overlap disease, and rare true polymyositis before selecting treatment; interpret autoantibodies in clinical context.
• Measure: Track strength and function, skin activity, swallowing, lung physiology, patient goals, glucocorticoid dose, and toxicity—never CK alone.
• Treat: Begin appropriate glucocorticoid induction and an early organ-matched steroid-sparing strategy; add rehabilitation, prophylaxis, vaccination, and bone protection from day one.
• Reassess: Before labeling disease refractory, exclude infection, cancer, nonadherence, drug toxicity, steroid myopathy, an incorrect diagnosis, and irreversible T1 fatty damage.
• Verify: VALOR studied brepocitinib 30 mg daily, not reposainib; confirm current FDA status and the final label before any clinical use, and keep FcRn and CAR-T approaches within evidence-appropriate investigational pathways.

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