Project Summary/Abstract: Multiple Sclerosis (MS) is the most common neurologic disabling disease among young adults, affecting over 400,000 people in the United States, 2.5 million worldwide and 20,000 under the care of the Department of Veterans Affairs. Most MS individuals are initially diagnosed with relapsing-remitting MS (RRMS) and then eventually transition to secondary progressive MS (SPMS). When MS individuals enter SPMS, neurologic deficits progressively worsen over time. Approximately 15% of people with MS are initially diagnosed with primary progressive MS (PPMS) and display increasing neurologic deficits without periods of relapse. Almost all the FDA approved therapeutics for MS are for patients with RRMS and there are very limited therapeutic options for people with progressive MS. A key cytokine/chemokine thought to drive the early inflammatory stage of MS to a chronic progressive phase is macrophage migration inhibitory factor (MIF). We have designed a potent biological construct called RTL1000 and a second-generation derivative, DRhQ, that bind tightly to the MIF receptor, CD74, and competitively inhibit MIF binding and it’s downstream signaling as well as inhibit T cell activation and release of IL-2. RTL/DRhQ treatment was also found to promote neuroprotection and reduce the severity of acute and chronic EAE, a mouse model of MS. RTL1000 was found to be safe and well tolerated at doses 60 mg in a Phase I safety trial in patients with either RRMS or SPMS. However, RTL1000 contains the extracellular domains of the MS risk factor, HLA-DR2 and as such, the FDA limited RTL1000 administration in the clinical trial to HLA-DR2 positive patients (~50% of total MS subjects). Our second generation construct, DRhQ, retains the potent immunomodulatory activity of RTL1000 but is HLA invariant and thus suitable for all patients. In order to treat both DR2 positive and negative individuals with progressive MS, we are proposing crucial preclinical studies of DRhQ and its mouse homologue, DRmQ, which will advance DRhQ towards a First- In-Human (FIH) Phase 1 clinical trial. In this Merit Review application, we will evaluate: 1) multi-compartmental pharmacokinetics; 2) validate relevant biomarkers, including infusion induced cytokine release, inhibition of phosphorylated extracellular-related kinase (pERK1/2) and related cytokines, and inhibition of IL-2 secretion induced by activated T cells; and 3) potential neutralizing activity of anti-drug antibodies against DRhQ. The data collected during this project will be used to support the filing of an Investigational New Drug (IND) application to the FDA for a FIH study. The previous success of RTL1000 in reaching a Phase 1 clinical trial gives us confidence that we will achieve success in Phase 1 as well as Phase 2 and 3 clinical trials with DRhQ.