This is an open-label, multi-center, non-confirmatory study to assess the safety, efficacy, and cellular kinetics of YTB323 in approximately 28 participants with Relapsing Multiple Sclerosis (RMS) with breakthrough disease activity during previous treatment with a highly efficacious therapy (BD-HET). The study design utilizes an ascending single dose design consisting of 3 sentinel cohorts followed by an expansion cohort.
Signed informed consent, and able to communicate well with the investigator and comply with the requirements of the study
Adequate renal, hepatic, cardiac, hematological, and pulmonary function
Male or female participants, ≥18 years to ≤60 years at screening, with diagnosis of RMS according to the 2017 McDonald diagnostic criteria Evidence of recent (i.e. within 1 year) breakthrough disease activity while at least 6 months on a highly efficacious therapy (any of the following): rituximab (Rituxan®), ocrelizumab (Ocrevus®), natalizumab (Tysabri®), ofatumumab (Kesimpta®), ublituximab (Briumvi®) or evidence of breakthrough disease activity within 2 years after the latest alemtuzumab infusion (Lemtrada®).
Confirmed Clinical MS relapse
Diagnosis of primary progressive multiple sclerosis (PPMS) according to the 2017 revision of the McDonald diagnostic criteria at screening
History of or current clinically significant CNS disease (e.g. stroke, traumatic brain or spinal injury, history or presence of myelopathy) or neurological disorders which may mimic MS or ICANS at screening
Evidence of clinically significant cardiovascular (such as but not limited to myocardial infarction, unstable ischemic heart disease, New York Heart Association (NYHA) Class III/IV left ventricular failure, arrhythmia and uncontrolled hypertension within 6 months prior to screening), neurological disorders other than MS (including seizure disorders even when well controlled), psychiatric, pulmonary (including, history of or active severe respiratory disease, including Chronic Obstructive Pulmonary Disease, interstitial lung disease or pulmonary fibrosis), renal, hepatic, endocrine, metabolic (e.g. severe hypoproteinemia due to nephrotic syndrome), hematological disorders or gastrointestinal disease that, in the investigator's opinion, would compromise the safety of the participant, interfere with the interpretation of the study results or otherwise preclude participation or protocol adherence of the participant, prior to screening
Have donated blood or experienced a loss of blood > 400 mL within 3 months prior screening, or longer if required by local regulations