Efgartigimod (formerly ARGX-113) Indications
gMG is a rare and chronic autoimmune disease where IgG autoantibodies disrupt communication between nerves and muscles, causing debilitating and potentially life-threatening muscle weakness.
In MG, IgG autoantibodies either bind and occupy or cross-link and internalize the receptor on the muscle cells, thereby preventing the binding of acetylcholine, the signal sent by the nerve cell. In addition, these autoantibodies can cause destruction of the neuromuscular junction by recruiting complement, a potent cell-destroying mechanism of the human immune system. The muscle weakness associated with MG usually presents initially in ocular muscles and can then spread into a generalized form affecting multiple muscles, known as gMG. Approximately 85% of people with MG progress to gMG within 24 months (source: Behin et al. New Pathways and Therapeutics Targets in Autoimmune Myasthenia Gravis. J Neuromusc Dis 5. 2018. 265–277). MG in the ocular form initially causes droopy eyelids and blurred or double vision due to partial paralysis of eye movements. As MG becomes generalized it affects muscles in the neck and jaw, causing problems in speaking, chewing and swallowing. MG can also cause weakness in skeletal muscles leading to problems in limb function. In the most severe cases, respiratory function can be weakened to the point where it becomes life-threatening. These respiratory crises occur at least once in the lives of approximately 15% to 20% of MG patients. The U.S. prevalence of MG is estimated at approximately 20 cases per 100,000 (source: Philips et al, Ann NY Acad Sci. 2003).
Patients with confirmed AChR antibodies account for approximately 85% of the total gMG population (Behin et al. New Pathways and Therapeutics Targets in Autoimmune Myasthenia Gravis. J Neuromusc Dis 5. 2018. 265–277).
In May 2020, we announced positive topline results from the pivotal ADAPT clinical trial of efgartigimod for the treatment of gMG. The topline results from the ADAPT clinical trial showed that efgartigimod was well-tolerated, demonstrated clinically meaningful improvements in strength and quality of life measures, and provided the option of an individualized dosing schedule for gMG patients. The full Phase 3 ADAPT results were published in The Lancet Neurology in July 2021. The data from the ADAPT clinical trial and the subsequent open-label extension (ADAPT+) formed the basis for the regulatory approvals of VYVGART in the U.S., Japan and the EU.
ADAPT-SC Trial Design
In January 2021, we initiated ADAPT-SC, a registrational non-inferiority bridging study of SC efgartigimod for the treatment of gMG. The design of the bridging study is based on the demonstrated association between total IgG reduction and clinical benefit in gMG and incorporates feedback from the FDA. The study is comparing the PD effect of 1000 mg SC efgartigimod with 10 mg/kg IV efgartigimod. The primary endpoint is the percent change from baseline of total IgG levels measured at day 29.
On March 22, 2022, we announced positive topline results from the Phase 3 ADAPT-SC study. SC efgartigimod achieved the primary endpoint of total IgG reduction from baseline at day 29, demonstrating statistical noninferiority to VYVGART IV formulation in gMG patients. Based on these results, we announced the acceptance of a BLA by the FDA with a PDUFA target action date that was recently extended by three months to June 20, 2023.
Other Clinical Trials
We are currently evaluating alternative dosing regimens of efgartigimod IV in adult gMG patients in the ADAPT NXT clinical trial. In addition, a clinical trial of efgartigimod IV in pediatric gMG patients is ongoing. In 2022, a Phase 1 clinical trial evaluating the effect of efgartigimod or placebo on immune response to the polyvalent pneumococcal vaccine (PNEUMOVAX 23) was completed.
Primary ITP is an acquired autoimmune bleeding disorder, characterized by a low platelet count (<100×109/L) in the absence of other causes associated with thrombocytopenia. In most patients, IgG autoantibodies directed against platelet receptors can be detected. They accelerate platelet clearance and destruction, inhibit platelet production, and impair platelet function, resulting in increased risk of bleeding and impaired quality of life. Primary ITP is differentiated from secondary ITP, which is associated with other illnesses, such as infections or autoimmune diseases, or which occurs after transfusion or taking other drugs, such as cancer drugs. Platelet deficiency, or thrombocytopenia, can cause bleeding in tissues, bruising and slow blood clotting after injury. Patients may suffer from depression and fatigue as well as side effects of existing therapies, impairing their quality of life. Current therapeutic approaches include non-specific immunosuppression (e.g., steroids and rituximab), inhibition of platelet clearance (e.g., splenectomy, IVIg, anti-D globulin, and spleen tyrosine kinase inhibitor fostamatinib13) or stimulation of platelet production (e.g., thrombopoietin receptor agonist TPO-RA). Splenectomy remains the only treatment that provides sustained remission off therapy for one year or longer for a high proportion of patients. ITP affects approximately 72,000 patients in the U.S. (sources: Current Medical Research and Opinion, 25:12, 2961–2969; Am J Hematol. 2012 Sep; 87(9): 848–852; Pediatr Blood Cancer. 2012 Feb; 58(2): 216–220).
Phase 3 ADVANCE Clinical Trials
In the fourth quarter of 2019, the first of two registrational clinical trials, the ADVANCE Phase 3 clinical trial, was initiated to evaluate 10 mg/kg IV efgartigimod (VYVGART) for the treatment of primary ITP. The second registrational ADVANCE-SC clinical trial of 1000 mg SC efgartigimod for the treatment of primary ITP was initiated in the fourth quarter of 2020. Positive phase 3 topline data for the ADVANCE clinical trial were announced on May 5, 2022. ADVANCE was the second registrational clinical trial of VYVGART and the first Phase 3 clinical trial of a neonatal FcRn blocker in ITP. The ADVANCE clinical trial enrolled 131 adult patients with chronic and persistent ITP. Patients were heavily pretreated and 67% of patients had received three or more prior ITP therapies, including 59% who had prior thrombopoietin receptor agonist (TPO-RAs) experience, 34% with prior rituximab experience and 37% with a history of splenectomy.
The clinical trial met its primary endpoint demonstrating that a significantly higher proportion of patients with chronic ITP receiving VYVGART (17/78; 21.8%) compared to placebo (2/40; 5%) achieved a sustained platelet response (p=0.0316), defined as having platelet counts greater than or equal to 50x109/L on at least four of the last six scheduled visits between weeks 19 and 24 of treatment.
Key platelet-derived secondary endpoints showed VYVGART-treated patients had a statistically significant benefit compared to placebo on (1) cumulative number of weeks where platelet counts were at least 50x109/L in the chronic ITP population (p=0.0009) and (2) sustained platelet response in the overall population, including both chronic and persistent ITP patients (p=0.0108). Numerically fewer WHO-classified bleeding events occurred in treated patients throughout the clinical trial but the difference from placebo was not statistically significant. A higher proportion of treated patients in the overall population achieved a durable, sustained platelet response compared to placebo, defined as a sustained platelet response on at least six of the last eight scheduled visits between weeks 17 and 24 of treatment (p=0.0265), but was not considered statistically significant based on hierarchical testing.
Additional secondary endpoint data from the ADVANCE clinical trial are consistent with primary and secondary platelet-derived endpoints and provide additional context on metrics that often drive treatment decisions, including on International Working Group (IWG) responder status:
- 51.2% of VYVGART-treated patients were classified as IWG responders and 27.9% as complete responders compared to 20% of placebo patients as IWG responders and 4.4% as complete responders.
- IWG responders are defined as having a platelet count of at least 30x109/L, a two-fold increase in platelet count from baseline, and the absence of bleeding for two separate, consecutive weekly visits. Complete responders are patients with platelet counts of 100x109/L and the absence of bleeding for two separate, consecutive weekly visits.
Mean platelet count change from baseline: VYVGART-treated patients demonstrated a rapid onset of platelet count improvement with statistically significant separation from placebo observed at week one and maintained through 20 out of 24 weeks of the clinical trial.
Ten VYVGART-treated patients switched to a biweekly (every two weeks) dosing schedule after achieving platelet counts of 100x109/L for three out of four consecutive visits, compared to one placebo patient. Nine of the ten treated patients achieved a sustained platelet response.
VYVGART was well-tolerated in this 24-week study and the observed safety and tolerability profile was consistent with previous clinical trials.
SC efgartigimod is being evaluated in a second registrational clinical trial in ITP, ADVANCE-SC topline data are expected in the second half of 2023. The clinical trial design for ADVANCE-SC is the same as for ADVANCE but the target enrollment was increased based on the results of the Phase 3 ADVANCE clinical trial.
Phase 2 Trial
We completed a randomized, double-blind, placebo-controlled Phase 2 clinical trial to evaluate the safety, efficacy and PK of efgartigimod in 38 adult primary ITP patients.
Full results from the Phase 2 clinical trial were published in the peer-reviewed American Journal of Hematology. Efgartigimod was well-tolerated and showed a correlation of reduced IgG levels, increased platelet counts and reduced bleeding in ITP patients.
The primary endpoint analysis demonstrated efgartigimod to be well-tolerated in all patients, with most treatment emergent adverse events (TEAEs) observed characterized as mild (Common Terminology Criteria for Adverse Events grading 1 and 2). There were no dose-related safety observations and the safety profile was consistent with previous observations in healthy volunteers and MG patients. No increased risk of infection was apparent in the efgartigimod-treated groups compared to the placebo group.
PV is an autoimmune disorder associated with mucosal and skin blisters that lead to pain, difficulty swallowing and skin infection. This chronic, potentially life-threatening disease is triggered by IgG autoantibodies targeting desmoglein-1 and -3, which are present on the surface of keratinocytes and important for cell-to-cell adhesion in the epithelium. Autoantibodies targeting desmogleins result in loss of cell adhesion, the primary cause of blister formation in PV. Similar to MG and ITP, disease severity of pemphigus correlates to the amount of pathogenic IgGs targeting desmogleins. Currently, there are an estimated 19,000 pemphigus patients in the U.S., of which an estimated 13,100 patients are suffering from PV. Several disease activity measurements exist for the clinical evaluation of PV patients, including the pemphigus disease area index (PDAI), autoimmune bullous skin disorder intensity score, and the PV activity score (PVAS). The PDAI is reported to have the highest validity and is recommended for use in clinical trials of PV.
Phase 3 ADDRESS Clinical Trial
In the fourth quarter of 2020, the registrational ADDRESS clinical trial was initiated of SC efgartigimod for the treatment of PV and PF. This is a randomized, double-blinded, placebo-controlled study, where the objective is to assess efficacy, safety and tolerability in up to 150 newly diagnosed or relapsing patients with moderate to severe pemphigus. Patients are randomized to receive either SC efgartigimod or placebo for 30 weeks. Patients start on concomitant steroids based on what we determine to be the optimized dosing regimen from the Phase 2 study. The primary endpoint will assess the proportion of patients who achieve complete remission on a minimal steroid dose at 30 weeks. The ADDRESS clinical trial will evaluate efficacy and safety, including the potential to drive fast onset of disease control and complete remission and the ability to taper corticosteroids. A relevant minority portion of the patients in the ADDRESS clinical trial are participating at sites in Ukraine or Russia. Following a risk assessment relating to the conflict between Russia and Ukraine, we increased target enrollment, which delayed expected topline data of SC efgartigimod for PV and PF to the second half of 2023.
Phase 2 Trial
We completed an open-label Phase 2 adaptive clinical trial in which, through sequential cohorts, 34 patients were dosed at 10 or 25 mg/kg IV efgartigimod (VYVGART) with various dosing frequencies, as monotherapy or add-on therapy to low dose oral prednisone. The primary endpoint of the clinical trial was safety and tolerability. The full Phase 2 clinical trial results were published in The British Journal of Dermatology.
In this clinical trial, we observed:
- a favorable tolerability profile, consistent with data from previous efgartigimod studies and those adverse events were mostly mild;
- a major decrease in serum total IgG and anti-desmoglein autoantibodies and correlated with improved PDAI scores;
- that 90% (28/31) of patients demonstrated early disease control; median time to disease control for monotherapy and combination therapy was 17 days;
- complete clinical remission in 64% (14/22) of patients receiving optimized prolonged treatment with efgartigimod in combination with a median dose of 0.26 mg/kg/day prednisone within 2–41 weeks; and
- a favorable tolerability profile, consistent with data from previous efgartigimod studies.
Novel translational data from the open-label Phase 2 study of efgartigimod for the treatment of PV that further support the potential role of FcRn blockade and potential of efgartigimod in autoimmune skin blistering disorders were published in the journal Frontiers of Immunology and presented during the Society for Investigative Dermatology annual meeting in May 2022.
CIDP is a chronic autoimmune disorder of peripheral nerves and nerve roots caused by an autoimmune-mediated destruction of the myelin sheath, or myelin producing cells, insulating the axon of the nerves and enabling speed of signal transduction. The cause of CIDP is unknown, but abnormalities in both cellular and humoral immunity have been shown. CIDP is a chronic and progressive disease: onset and progression occur over at least eight weeks in contrast with the more acute Guillain-Barré-syndrome. Demyelination and axonal damage in CIDP lead to loss of sensory and/or motor neuron function, which can lead to weakness, sensory loss, imbalance and/or pain. CIDP affects approximately 16,000 patients in the U.S.
Most CIDP patients require treatment and IVIg which is the preferred first-line therapy. Glucocorticoids and plasma exchange are used to a lesser extent as they are either limited by side effects upon chronic use, in the case of glucocorticoids, or invasiveness of the procedure and access, which is restricted to specialized centers in case of plasma exchange. Alternative immunosuppressant agents are typically reserved for patients ineligible for or refractory to IVIg, glucocorticoids or plasma exchange.
ADHERE Clinical Trial
At the end of 2019, we initiated the registrational ADHERE clinical trial evaluating SC efgartigimod for the treatment of CIDP. The ADHERE clinical trial is a randomized, withdrawal study evaluating 1000 mg weekly SC efgartigimod expected to enroll approximately 130 patients. The clinical trial consists of an open-label Stage A followed by a randomized, placebo-controlled Stage B with a planned interim responder analysis after the first 30 patients enroll in Stage A. In order to enter Stage A and receive efgartigimod, both patients who are treatment-naïve or on therapy must first receive a confirmed diagnosis of CIDP by an independent panel of experts and demonstrate active disease. To show active disease, patients who are on current CIDP therapy have to demonstrate a minimal clinically meaningful worsening after treatment withdrawal based on at least one CIDP clinical assessment tool, including the Inflammatory Neuropathy Cause and Treatment Disability Score (INCAT Disability Score), Inflammatory Rasch-built Overall Disability Scale (I-RODS) or mean grip strength. To advance to Stage B, patients need to demonstrate a minimal clinically meaningful response to efgartigimod equivalent with the loss observed on the same efficacy scale on which worsening is observed during the withdrawal period. In Stage B, patients are randomized to either SC efgartigimod or placebo for up to 48 weeks. The primary endpoint is event-driven and based on the adjusted INCAT Disability Score in Stage B.
Interim Analysis from ADHERE Clinical Trial
In February 2021, we announced a “go” decision to transition into the second, placebo-controlled stage of this clinical trial based on a planned efficacy and safety assessment following the enrollment of 30 patients into the initial part of the ADHERE clinical trial. The ADHERE clinical trial is expected to enroll at least 130 patients in total to support potential registration of SC efgartigimod for the treatment of CIDP. The interim analysis achieved the pre-defined threshold for continuation, which was based on response rates seen in precedent clinical trials of current standard of care in CIDP. The decision to continue enrollment was confirmed by an independent data monitoring committee. In addition, the safety and tolerability data observed to date is consistent with that of efgartigimod in other clinical trials.
We expect to announce the topline data of the ADHERE clinical trial in the second quarter of 2023.
Idiopathic Inflammatory Myopathies (Myositis)
Myositis are a rare group of autoimmune diseases that can be muscle specific or affect multiple organs including the skin, joints, lung, gastrointestinal tract and heart. Myositis can be very severe and disabling and have a material impact on quality of life. Initially these Myositis were classified as either DM or polymyositis, but as the underlying pathophysiology of Myositis has become better understood, including through the identification of characteristic autoantibodies, new polymyositis subgroups have emerged. Two of these subtypes are IMNM and ASyS. Proximal muscle weakness is a unifying feature of each Myositis subset.
- IMNM is characterized by skeletal muscle weakness due to muscle cell necrosis. The muscle weakness is typically symmetrical – on both sides of the body – and affects proximal muscles including hips, thighs, upper arms, shoulder and neck. The muscle weakness can be severe and lead to difficulty in completing daily tasks. Characteristic autoantibodies of IMNM, include anti-signal recognition particle and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase autoantibodies.
- ASyS is characterized by muscle inflammation, inflammatory arthritis, interstitial lung disease, thickening and cracking of the hands (“mechanic’s hands”) and Raynaud phenomenon. Autoantibodies associated with ASyS attack tRNA synthetase enzymes and include anti-Jo-1 and anti-PL1 and PL-12 most commonly.
- DM is characterized by muscle inflammation and degeneration and skin abnormalities, including heliotrope rash, Gottron papules, erythematous, calcinosis and edema. DM is associated with Myositis-specific autoantibodies, including anti-Mi-2, anti-MDA-5, anti-TIF-1γ and others.
There are no current FDA-approved therapies for IMNM or ASyS. IVIg (Octagam 10%) was approved by the FDA for the treatment of DM in July 2021. Myositis patients are most often treated with high-dose steroids.
ALKIVIA Clinical Trial
We initiated the registrational ALKIVIA clinical trial of SC efgartigimod for the treatment of Myositis in the third quarter of 2022. The study plans to enroll approximately 240 patients in three Myositis subtypes, IMNM, ASys and DM. The study will be conducted in 2 phases, with an analysis of the Phase 2 portion of the clinical trial, including 30 patients of each subtype, followed by conduct of the Phase 3 portion of the clinical trial.
The primary endpoint is the total improvement score (TIS) at the end of the treatment period. Key secondary endpoints include response rates at the end of treatment, time to response, and duration of response in TIS, as well as change from baseline in individual TIS components. Other secondary endpoints include quality of life and other functional scores.
An interim analysis of the first 30 patients in each subset is expected in 2024.
BP is the most common autoimmune blistering disease and is driven by autoantibodies affecting the skin. The disease typically affects elderly people and early key symptoms are itch and rash and patients develop fluid-filled blisters during disease progression. The prevalence of BP is twelve per 100,000 adults and the incidence increases with age. BP is associated with a high disease burden and can have a significant impact on the quality of life of patients. The mortality of BP in the U.S. is 2.4% or higher than the mortality in the general population of the same age. There are currently no approved therapies available for BP. First line treatment consists of topical or systemic corticosteroids, which result in substantial morbidity and increased mortality, conventional immunosuppressants as corticosteroid-sparing agents, rituximab and IVIg.
BP is a well characterized autoimmune disease in which the binding of autoantibodies to hemidesmosomal proteins, BP180 and BP230, initiates a cascade of inflammatory events resulting in blister formation. BP180 and BP230 are involved in the stable attachment of keratinocyte to the underlying matrix. The autoantibody actions include mechanical disruption of keratinocyte adhesion and cytokine release. Immune complex formation initiates complement activation leading to the recruitment mast cells, neutrophils, eosinophils and other immune cells and to the release of proteases and inflammatory mediators. All these effects, which start with the binding of the autoantibodies, induce the blistering observed in BP.
We initiated the Phase 2/3 BALLAD registrational clinical trial evaluating SC efgartigimod in BP in the second half of 2022, in which we plan to enroll 160 patients.
The clinical trial population are newly diagnosed and relapsing patients within one year from diagnosis. Patients will be randomized 1-to-1 to receive efgartigimod or placebo for total duration of 36 weeks. The primary endpoint is the proportion of participants in complete remission while off oral corticosteroids for at least eight weeks at week 36. Secondary endpoints relate to cumulative steroid doses, IGA BP score, time to achieving control of disease activity, change from baseline in average itch, and quality of life measures. In our Half Year 2022 report, we announced that the registrational BALLAD clinical trial is ongoing of SC efgartigimod for BP with interim analysis planned of first 40 patients in 2024.
New Efgartigimod Indications
We are also evaluating four indications in proof-of-concept clinical trials through our partnerships with Zai Lab and IQVIA:
- MN is an autoimmune, glomerular disease and the most frequent cause of nephrotic syndrome. MN is characterized by thickening of the glomerular capillary walls caused by immune complex deposition. 70% of MN patients have IgG autoantibodies against PLA2R. In patients without PLA2R autoantibodies, there can be detectable anti-THSd7A or anti-NELL1 antibodies. 20–30% of patients progress to end-stage renal disease. There are no current approved therapies for MN.
- LN is a glomerulonephritis and one of the most severe and common organ manifestations of the autoimmune disease systemic lupus erythematosus (SLE). LN is a substantial cause of morbidity and death among patients with SLE. Autoantibodies associated with LN include anti-dsDNA and anti-nuclear antibodies. 5–20% of LN patients progress to end-stage renal disease. Oral corticosteroids and broad immunosuppressants are current standard of care but are not uniformly effective.
- Primary SjS is a systemic autoimmune disease of the exocrine glands that can affect salivary and lacrimal glands, mostly, and result in severe dryness of mucosal surfaces, primarily in the eyes and mouth. In addition to sicca symptoms, patients can experience significant fatigue, chronic pain, major organ involvement, neuropathies and lymphomas. Autoantibodies are present in the majority of patients and include antinuclear antibodies and antibodies against Primary SjS-related antigen A and B (anti-SSA Ro and SSB La). There are no current FDA-approved therapies and patients are most often treated with IVIg, in severe cases, or eyes drops and corticosteroids in more mild to moderate patients.
- PC-POTS has been emerging after resolution of COVID-19 infection in previously healthy patients. PC-POTS is a disorder of the autonomic nervous system that is characterized by a rise in heart rate when moving to a standing position and additional symptoms of shortness of breath, headache, fatigue, poor concentration, weakness and anxiety. The large majority of patients are women between 15 and 50 years of age. There is a strong association of PC-POTS to activating autoantibodies to autonomic G-protein coupled receptors, including the β1 and β2-adrenergic receptors and M2 and M3 muscarinic receptors. There are no current FDA-approved therapies and symptomatic treatments focus on blood volume, kidney sodium levels, heart rate reduction and vessel constriction.
Zai Lab Limited
Our Zai Lab strategic collaboration allows us to accelerate development of efgartigimod into new autoimmune indications with Zai Lab taking operational leadership of the Phase 2 proof-of-concept clinical trials.
Zai Lab initiated the Phase 2 proof-of-concept clinical trials in 2022 in MN and LN, which both fall within our emerging nephrology franchise.
On December 2, 2021 we entered into a strategic asset development agreement (Asset Development Agreement) with IQVIA. Pursuant to the Asset Development Agreement, IQVIA shall perform asset and indication development services for efgartigimod through an advanced outsourcing model. Such services include, but are not limited to, overall product indication development strategy, design of clinical trial protocol, set-up, execution and oversight of clinical development plans for an indication for efgartigimod selected by us.
To enable and encourage fast and innovative delivery of the services by IQVIA, the Asset Development Agreement contains an innovative earn-back and bonus plan based upon the performance of IQVIA.
Primary SjS and PC-POTS are the first indications we identified to be further developed under the Asset Development Agreement.
In 2022, IQVIA launched the Phase 2 clinical trials in Primary SjS and PC-POTS.
Additional Efgartigimod Indications
In January 2023, we announced our plans to launch clinical trials in three new indications including a registrational clinical trial in TED and proof-of-concept clinical trials in AV and AMR.