Our platform

RETROFIT is anchored in understanding the root causes of resistance (Oncology+) — and built to deliver the therapies that overcome those mechanisms.

The platform discovers and develops first-in-class multi-specific antibody drug candidates against refractory diseases by applying a logic-gated interrogation engine to real-world multi-omics data — turning mechanistic causality, not opportunistic target pairing, into the starting point for drug discovery.

Retrofit was co-founded by four specialized labs at KU Leuven, combining immuno-oncology, antibody engineering, AI/machine learning and computational expertise into a single, closed-loop discovery platform.

The platform offers end-to-end integrated delivery from target combination identification through drug candidates ready for IND-enabling studies.
Refractory disease focus
Deeply annotated multi-omics data combined to logic-gated methods
Multispecific antibodies
First-in-class VHH-based multispecific Ab discovery and engineering
Proprietary AI pipeline
We target patients existing treatments leave behind
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Every project starts from a clearly defined unmet need.

Deeply annotated multi-omics data are used to isolate root causes of resistance; logic-gated methologies then define the target combinations that overcome them.



Public datasets combined with proprietary, clinically-annotated human data, refined through immunologist- and clinician-in-the-loop cycles, and interrogated with in-house "causality-friendly" AI/ML to generate better insights, hypothesis and predictions. Adaptable to agentic and generative AI as the field evolves.



Logic-gated target selection is designed to produce combinations where efficacy depends on simultaneous engagement — a property difficult to replicate with the combination-therapy regimens that dominate solid tumor I-O today.

In-house, best-in-class antibody engineering, from VHH discovery and multi-specific antibody engineering to translational validation

Retrofit leverages a state-of-the-art toolbox to yield optimized and functionally characterized multi-specific antibodies tailored to the original clinical unmet need they will address.



Data packages are built aiming towards maximum human translatability: in vivo models are rationally selected via systems/AI-driven reverse translation based on their relevance to the human disease, and mode-of-actions are determined using an array of complementary translational human models. To increase clinical translation, for each asset, an AI-driven digital pathology-based biomarker is developed to guide future clinical development and allow for biology-informed patient stratification.



Critically, this is not a linear, one-way pipeline: wet-lab outcomes from target validation, preclinical efficacy/safety studies, and biomarker characterization are systematically fed back to iteratively refine our data-lake interrogation, target mining, and logic-gating approaches with each asset. This lab-in-the-loop architecture means the platform's predictive accuracy increases over time.

Our therapeutic candidates are engineered to target underserved patient populations and unaddressed biology, serving the mission to continually expand the treatment options available to patients.

Next-generation biologics are emerging as a promising modality across diseases where monospecific approaches have hit a ceiling, and where complex resistance mechanisms demand multimodal strategies. 


Current multi-specific targets remain heavily biased towards cancer cell – lymphocyte interactions, excluding the largest patient demographic: refractory tumors known to be enriched in macrophage/stromal cells and depleted or excluded of T cells.

RETROFIT's approach does more than expand the addressable target space — it also accelerates development and improves the probability of success for these innovative drugs.



Oncology is the platform's primary focus, but the discovery engine is disease-agnostic — built to target the same resistance biology wherever it appears, including in chronic inflammatory and autoimmune disease

Numbers

Platform at a glance

3.5M+
Single-cells across 22 I-O studies and 500 patients.
3,500+
Bulk transcriptomic samples with I-O response data.
180+
Visium spatial samples, incl. 62 confirmed I-O responders.
20+
Solid tumor indications captured in the data lake.
4 + 1
Co-founding KU Leuven labs and one antibody center powering the platform.
In-house
VHH-based MsAb generation and engineering capabilites.
3
Assets moving toward IND and 1 proven obligate tri-specific.
Go-to-Market
Non-dilutive funding secured through to New Co creation.
Pipeline

Programs in development.

RETROFIT is advancing a pipeline of first-in-class multi-specific antibodies (msAbs) across multiple stages of preclinical development, with the potential to treat a broad range of solid tumor indications and to extend into additional disease areas beyond oncology.
RF-001
Discovery
Trispecific Ab
Refractory solid tumors
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Pipeline program

RF-001

RF-001 is an investigational, first-in-class tri-specific antibody engineered to selectively target the newly discovered tumor-specific macrophage subset that co-expresses TIM3, VISTA and CSF1R.
This population represents an evolutionarily conserved niche of immuno-resistant tumor-associated macrophages (TAMs) identified in refractory tumors across both human and mouse immunotherapy-resistance settings (Vanmeerbeek et al., Sci Adv 2024).
Preclinical studies have demonstrated that only an obligatory tri-specific engagement can drive TAM activation and lead to eradication of refractory tumors in vivo.
The programme is currently in lead optimization stage.

RF-002
Discovery
Bispecific Ab
Refractory solid tumors
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Pipeline program

RF-002

RF-003
Discovery
Bispecific Ab
Refractory solid tumors
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Pipeline program

RF-003

Our team

Built to develop the medicines patients need

Retrofit is powered by an experienced management team, backed by founders and advisors whose world-class expertise spans immunology, translational research and drug development - united by a shared mission to decode and overcome immuno-resistance.
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News
Latest Updates
Research moves fast. These updates track where Retrofit's programs stand, from new preclinical data to platform milestones and conference presentations as we advance toward spin-off.
Publications

Peer-reviewed science.

Scientific posters and publications from the Retrofit platform and its founding laboratories. Publications available on demand.
Science Advances 2024
Targeting conserved TIM3+VISTA+ tumor-associated macrophages overcomes resistance to cancer immunotherapy
Vanmeerbeek et al.
To publication
Nature communications 2026
Engineering trispecific IL-2 receptor agonistic antibodies through geometry optimization for enhanced Treg targeting
Lykhopiy et al.
To publication
Cell discovery 2023
Single cell dynamics of tumor specificity vs bystander activity in CD8+ T cells define the diverse immune landscapes in colorectal cancer
Borras et al.
To publication
Nature Medicine 2024
A spatial architecture-embedding HLA signature to predict clinical response to immunotherapy in renal cell carcinoma
Kinget et al.
To publication
Science Translational Medicine
Multiomics and spatial mapping characterizes human CD8+ T cell states in cancer
Naulaerts et al.
To publication
Contact
Let's connect.
Whether you are an investor exploring early-stage opportunities, a pharma company looking for strategic partnership or an academic group interested in future collaboration, we’d love to hear from you.
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KU Leuven · Herestraat 49 3000 Leuven, Belgium
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