Climb Bio (NASDAQ:CLYM) used a presentation at the Leerink Partners Global Healthcare Conference to outline its strategy around two immune-focused programs and to preview a series of data readouts expected in 2026. Chief Executive Officer Aoife Brennan and Chief Financial Officer Susan Altschuller described 2025 as a “year of execution” focused on manufacturing, assays, and study setup, positioning the company for what they called a “very rich data year” in 2026.
Company background and focus on B-cell biology
Brennan said Climb was formed in 2024 “within the Eliem Therapeutics ticker” and was built around the view that, while newer modalities have helped validate key B-cell targets, there remains significant opportunity for monoclonal antibodies due to scalability and market access advantages. The company began with one lead program, budoprutug (referred to as “budo” in the discussion), a CD19 monoclonal antibody intended to deplete B cells, and in-licensed a second asset, CLYM116, in early 2025.
Rationale for CD19 vs. CD20 in autoimmune and inflammatory diseases
She pointed to clinical data from Amgen’s UPLIZNA as evidence supporting the CD19 approach, including efficacy in myasthenia gravis, an indication she said has seen CD20 failures. Brennan added that observing UPLIZNA’s commercial performance in myasthenia gravis will be an important datapoint for Climb.
When comparing Climb’s CD19 antibody with UPLIZNA, Brennan emphasized differences in development strategy more than molecular specifics. Climb is pursuing a subcutaneous (subq) formulation and is initially targeting indications that have not been evaluated with UPLIZNA, citing “tremendous” remaining white space for CD19 monoclonals.
Budoprutug: subcutaneous bridge and three clinical “chapters”
Climb plans to report subq formulation data for budoprutug in the first half of 2026. Brennan said the formulation work has reached concentrations of 175 mg/mL, and the near-term question is whether subq dosing can achieve B-cell depletion consistent with intravenous exposure. In the healthy-volunteer study, doses are lower than full depletion levels, and the company is looking for measurable depletion in a range consistent with IV experience to support a path into patient studies at doses expected to fully deplete B cells.
In the second half of 2026, Climb expects initial readouts from three budoprutug studies:
- Primary membranous nephropathy (PMN): Brennan framed PMN as a relatively prevalent immune-mediated glomerular disease with no currently approved therapy and substantial off-label treatment use. She cited legacy data indicating B-cell depletion and PLA2R (immunologic) remission, with 60% of patients achieving complete renal response (proteinuria <0.3 grams per 24 hours). Climb also presented long-term follow-up at Kidney Week, noting that three of four patients with available data required no further immunotherapy over three years. The ongoing study is designed as a dose-escalation effort with a larger and more commercially relevant moderate-to-severe population. Brennan said the 2026 dataset will be “relatively early,” emphasizing biomarker and safety readouts and trends in proteinuria rather than one- or two-year clinical endpoints. She said a key goal is replicating the earlier signal in “multiples” of the initial small dataset.
- Immune thrombocytopenia (ITP): The company is studying chronic or persistent ITP patients who have failed available therapies, with a mix of prior exposure to rituximab and thrombopoietin (TPO) agents. Brennan highlighted platelet response, B-cell depletion, and durability as key measures, describing the target as a third-line population where placebo response is consistently low and platelet response is an approvable endpoint. The study includes three dose cohorts with six patients each.
- Systemic lupus erythematosus (SLE): Brennan said Climb’s SLE study is a single-dose design intended to assess translational biomarkers rather than clinical endpoints. The company aims to test whether a “naked monoclonal” can drive biomarkers suggestive of immune “reset” similar to what has been seen with CD19-directed CAR-T or T-cell engagers. She said clinical interpretation in early SLE studies can be difficult, making biomarker comparisons across modalities particularly important for next-step decisions and for assessing whether treatment could be episodic or chronic.
Discussing the broader CD19 landscape, Brennan suggested future autoimmune care may involve multiple modalities and sequences, with some patients achieving durable remission while others require repeat treatment. She also described a potential role for monoclonals as repeatable therapies, including scenarios where patients relapse after CAR-T and may not be candidates for frequent repeat cellular therapy.
CLYM116: APRIL-only “sweeper” antibody and IgA nephropathy focus
Turning to CLYM116, Brennan said Climb evaluated global opportunities in APRIL-only and BAFF/APRIL biology, setting a bar that APRIL-only would need a rationale to be “better” than sibeprenlimab and BAFF/APRIL would need a rationale to outperform povetacicept. Climb in-licensed CLYM116 in January 2025 and conducted a head-to-head non-human primate (NHP) study, citing the translatability of NHP biomarker data in this class. Altschuller said the key differentiation is the “sweeper” mechanism: pH-dependent binding allows APRIL to be bound extracellularly, internalized, released for degradation in the endosome, and the antibody recycled via FcRn—potentially enabling multiple APRIL molecules to be cleared per antibody. The company also noted half-life extension and a LALA mutation.
Climb expects healthy-volunteer data for CLYM116 around midyear 2026. The company will evaluate pharmacokinetics, dosing interval, IgA reduction, and immunogenicity. Brennan said other agents have shown roughly 50% IgA reduction and noted that the NHP work showed up to 80%, while cautioning that human data will be needed. She also highlighted the importance of anti-drug antibodies in a long-term treatment setting, noting that sibeprenlimab’s label includes a “decent” ADA rate and that patients with ADA had lower efficacy in terms of proteinuria reduction. Climb believes CLYM116 may differ based on its binding epitope and expects the healthy-volunteer study to provide information relevant to that hypothesis.
On market dynamics in IgA nephropathy, Brennan said she expects the category to evolve toward achieving low absolute proteinuria targets (citing 0.3 grams per day as a clinical goal), with physicians potentially escalating therapy based on patient response. She said current data do not show an advantage to adding BAFF to APRIL, while noting theoretical safety risks such as hypogammaglobulinemia and cytopenias for BAFF/APRIL approaches, and she said more data are needed, including upcoming povetacicept results and early real-world experience as sibeprenlimab is launched. Climb identified IgA nephropathy as the lead indication for CLYM116 and mentioned Sjögren’s as an area of interest for potential expansion, pending profile validation.
Financial position, spending priorities, and business development
Altschuller said the company ended the fourth quarter with $161 million in cash and runway into 2028. She said the runway supports current programs but does not include “pivotal trial ramp-up” for indications such as PMN or IgA nephropathy. Near term, she said budoprutug has more ongoing trials and therefore a larger expense base, while describing both PMN and ITP pivotal studies as potentially smaller (around 150 patients) and calling IgA nephropathy larger but still manageable.
Management also emphasized operational synergies across the pipeline, particularly in kidney-focused indications, including overlapping sites, assays, and infrastructure. On business development, Brennan said Climb remains open to in-licensing additional earlier-stage assets—similar to the approach used for CLYM116—while remaining disciplined and focused rather than expanding into unrelated therapeutic areas.
About Climb Bio (NASDAQ:CLYM)
Climb Bio Therapeutics, Inc is a clinical-stage biotechnology company focused on the discovery and development of engineered protein therapeutics for the treatment of cancer and immune-mediated disorders. The company’s mission centers on designing biologics with enhanced specificity and functional activity to engage key cellular targets and improve patient outcomes in areas of high unmet need.
At the heart of Climb Bio’s approach is its proprietary protein engineering platform, which combines mammalian cell display, directed evolution and computational modeling.
