We are a clinical-stage biopharmaceutical company developing next-generation biotherapeutics for immune-mediated diseases with high unmet need. Our lead pipeline candidates target commercially validated pathways and are designed through our ATTOBODY biologics platform to deliver improved treatments relative to the current standards of care. Leveraging our ATTOBODY platform, we have nominated three product candidates within our first two years, including one currently in the clinic, ATTO-1310. ATTO-1310 is an ATTOBODY-based therapeutic targeting interleukin-31 (IL-31) that completed dosing in a Phase 1 clinical trial in healthy volunteers (HVs) and patients in the first quarter of 2026. ATTO-2306 is an ATTOBODY-based bispecific targeting interleukin-13 (IL-13) and IL-31 that is in investigational new drug (IND)-enabling studies, and we expect to commence a Phase 1 clinical trial in the first half of 2027. Lastly, ATTO-1091 is our trispecific ATTOBODY-based Fc fusion protein that is designed to block TL1A, IL-23 and integrin a4ß7 simultaneously, and is currently in IND-enabling studies. All of our product candidates have been internally discovered using our ATTOBODY biparatopic biologics platform, which we have in-licensed from Alamar Biosciences, Inc. (Alamar). Our ATTOBODY platform uses an evolution-driven, high-throughput process which allows for rapid discovery and creation of a high diversity of potential product candidates. Our initial focus for ATTOBODIES has been to develop novel biotherapeutics targeting highly synergistic, clinically and commercially validated pathways where early data indicates the potential of our candidates to deliver next-generation treatments relative to the current standards of care. Our early-stage discovery efforts have further expanded our pipeline to additional complex biologics, including conditional “AND” gate bispecifics directed against novel targets, which are historically difficult to develop with conventional antibody technology. ATTO-1310 is a novel ATTOBODY-based Fc-fusion protein therapeutic that inhibits IL-31 and is currently in a Phase 1 clinical trial in HVs and patients suffering from chronic pruritus and high-itch atopic dermatitis (AD). IL-31 is commonly known as the “itch cytokine” and is upregulated in a host of pruritic diseases. We plan to evaluate ATTO-1310 for the treatment of chronic pruritic diseases such as chronic pruritus of unknown origin (CPUO), high-itch AD, cholestatic pruritus in primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) and chronic kidney disease-associated pruritus (CKD-aP), also known as uremic pruritus, in subsequent clinical trials. Beyond individual diseases, we also intend to pursue a potential pan-pruritic disease regulatory development path for patients with elevated levels of IL-31. Our initial clinical data demonstrated that ATTO-1310 has been well tolerated with low immunogenicity and pharmacokinetic (PK) and target engagement data supporting the possibility of an extended dosing regimen in human patients. Initial data from our Phase 1b clinical trial of ATTO-1310 in patients with chronic pruritus and high-itch AD showed rapid, deep itch relief in both patient populations and consistent lesion control for patients with high-itch AD. We believe ATTO-1310 has the potential to offer patients fast and deep itch relief, a favorable tolerability profile and convenient subcutaneous (SC) dosing once every three months. ATTO-2306 is an ATTOBODY-based, half-life extended, immunoglobulin-G (IgG)-fusion protein therapeutic that inhibits IL-13 and IL-31. IL-13 and IL-31 reside in the only two clinically and commercially validated pathways in AD, and we believe that blocking them in a bispecific format offers a novel approach and a high likelihood of achieving differentiated treatment effect and extended dosing by avoiding the reverse dose-efficacy effect seen for IL-31Ra and the target-mediated drug disposition (TMDD) observed in treatments targeting IL-4Rα. We believe ATTO-2306 has the potential to provide a new standard of care for the treatment of AD and other immune-mediated skin diseases, such as chronic spontaneous urticaria (CSU) and prurigo nodularis (PN), by offering favorable lesion and itch control, as well as significantly improved convenience compared to currently available treatments. Independent third-party market research studies1 commissioned by us estimated that by 2035 AD will affect 21 million adults and 10 million pediatric patients in the United States, with approximately one-third of AD patients having moderate-to-severe disease. We expect to commence a Phase 1 clinical trial for ATTO-2306 in the first half of 2027. ATTO-1091 is a trispecific ATTOBODY-based Fc-fusion protein therapeutic that inhibits TL1A, IL-23 and integrin α4ß7, and is currently undergoing IND-enabling studies. TL1A, IL-23and integrin α4ß7 all play distinct roles in inflammatory bowel disease (IBD) pathophysiology, contributing to inflammation and fibrosis in the gut and intestinal tissue. We believe that ATTO-1091 has the potential to improve upon existing induction and maintenance therapies for IBD by inhibiting three clinically validated pathways with preserved binding affinity and potency of each individual arm in the trispecific format. We plan to initiate a Phase 1 clinical trial for ATTO-1091 in the first half of 2027, subject to IND clearance. Our principal executive offices are located in San Carlos, California.
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