Our science

Rondo Therapeutics is pioneering next-generation CD28 bispecific antibodies to deliver maximum clinical benefit with minimal side effects.

Clinical landscape

Untapped clinical opportunity with immune- cell engaging bispecific antibodies

Immune checkpoint inhibitors, cell therapies, and ADCs are treatment options available for solid tumors, but each of these modalities brings its own challenges. In an adaptive immune response, T-cell activation is initiated when the T-cell receptor (CD3) is engaged. This immune response is then sustained by the engagement of co-stimulatory receptors like CD28 and CD137. Activation of T-cells through CD3 is often referred to as Signal 1 and co-stimulation as Signal 2. CD3 T-cell engagers, delivering Signal 1 alone, show efficacy as monotherapies in liquid tumors. However, treating solid tumors requires Signals 1 and 2 to overcome the immunosuppressive microenvironment.

Targeted Modalities




Checkpoint Inhibitors

30% response rate,
heme & Solid

Autoimmune & inflammatory toxicity

Low Response Rate

CAR-T Cell Therapy

80% Response Rate,
Heme only

CRS & On-target, off-tumor Toxicity

Limited Patient Access


30-40% Response Rate, Heme & Solid

Toxicity related to payload toxin

Sub-Optimal Efficacy at Low Tumor antigen Densities, Dose limiting Toxicities

CD3 T-Cell Engagers

60-80% Response Rate,
Heme only

CRS & on-target, off-tumor toxicity

low Response Rate
in Solid tumors

Swipe to Explore

T-cells in immune-primed tumors
have activated signal 1 ​

Strategy - Boost signal 2 with
​CD28 bispecific antibody (+/- SoC)​

T-cells in immune-cold tumors
lack​ signals 1 & 2

Strategy - Deliver both signals 1 and 2 with ​
CD28 and CD3 bispecific combinations​

Our approach

Tuned and targeted CD28 bispecific antibodies

T-cell engagers harness the immune system to combat cancer by targeting tumor associated antigens (TAAs) on cancer cells then recruiting and activating T-cells to unleash potent anti-tumor responses.

While CD3 T-cell engagers are effective treatments for blood cancers, solid tumors present additional obstacles due to the immune-suppressive tumor microenvironment.

Enter CD28, a key co-stimulatory receptor essential for robust and sustained T-cell-mediated tumor clearance. First-generation, super-agonist monoclonal antibodies targeting CD28 stimulated systemic T-cell activation leading to severe dose-limiting toxicities in the clinic.

Stimulating CD28 with tumor-targeted bispecific antibodies delivers a boost of signal 2 boost to T-cells at the site of the tumor while avoiding super-agonist activity.

CD28 has many features of an ideal co-stimulatory target for bispecific therapies because CD28 is constitutively expressed on active and resting T-cells and requires lower tumor antigen density for robust bispecific-induced tumor clearance.

Our Strategic advantage

Designed to maximize the therapeutic window

Maintaining efficacy while reducing toxicity is Rondo Therapeutics’ strategy, providing clinicians flexibility with dosing strategies and combination regimens.

Bispecific antibodies with wide therapeutic windows for the safe and effective treatment of solid tumors

Immune-cell engaging mechanism of action

Sustained T-cell mediated tumor cell killing

Maximum therapeutic window

  • Efficacy in an immunosuppressed environment
  • Avoidance of T-cell activity in healthy tissue with low levels of antigen expression
  • Low immunogenicity risk


Our proprietary discovery approach

NGS-based discovery enables rapid characterization and development of highly-diverse binding arm collections which are critical for high-throughput lead optimization.

Using a common-light chain format enables flexible pairing of immune effector and tumor targeting arms.

Our proprietary high-throughput functional and biophysical assays optimize for desired properties and rapidly identify the best bispecific antibody development candidates.

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Partnerships, advisory, and investment opportunities

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