Rarefied Pipeline

Advancing the Next Generation of Autoimmune Therapies.

Rarefied Bio is building a pipeline around our new approach to rebalancing the immune system. Our lead candidate, RB201, has successfully completed a Phase 1 human trial, and shows broad preclinical efficacy across multiple autoimmune models.

Autoimmune diseases affect hundreds of millions worldwide, yet most treatments today are inadequate. Patients often face chronic flares, incomplete control, and reduced quality of life.

The Problem

For decades, treatments have focused on broadly suppressing the immune system — from cytokine blockers to JAK inhibitors. While they can bring temporary relief, these approaches often come with significant safety risks and limited long-term efficacy.

Inadequate Approaches

Rarefied Bio targets a key upstream regulator of immune activation. By selectively “re-tuning” misfiring immune cells, RB201 restores immune balance while preserving the body’s natural defenses — offering the potential for durable efficacy without systemic risk.

Our Solution

Rarified Pipeline

DISCOVERY

PRE-CLINICAL

PHASE 1

PHASE 2

RB201

PHASE 1 COMPLETE

First-in-class oral inhibitor.
Successfully completed Phase 1 human trial.
Targets the upstream drivers of autoimmunity without compromising defenses.

RB202

Autoimmunity

Our goal is to translate precise, upstream control of immune activation into meaningful therapies across a spectrum of autoimmune diseases — from rheumatoid arthritis and lupus to inflammatory bowel disease and psoriasis.