Project Background
A biotechnology research team was exploring whether an androgen receptor (AR)-enriched cellular context could be used to recruit an essential effector protein and induce selective functional impairment in AR-positive prostate cancer models. The client had several AR-binding scaffolds with submicromolar cellular activity but lacked a clear strategy for effector selection, linker design, ternary complex evaluation, and matched cell-line validation. The main goal was to generate a focused RIPTAC series that could distinguish target-dependent activity from nonspecific cytotoxicity.
Our Support
BOC Sciences first reviewed the AR ligand structures and selected two attachment vectors with minimal predicted disruption to AR binding. We then evaluated three effector ligand options based on intracellular localization, ligand tractability, and measurable functional endpoints. A 24-molecule design matrix was created using alkyl, PEG-containing, and semi-rigid heterocyclic linkers ranging from 8 to 18 atoms. After synthesis, binary binding was evaluated first, followed by a proximity assay adapted from ternary complex workflows. Six compounds showed measurable target-effector proximity signals, and two analogs displayed stronger activity in AR-high cells than in AR-low comparator cells. The best-performing analog showed a clear concentration-dependent functional response below 300 nM in the AR-high model, while linker-shortened analogs lost activity despite retaining partial binary binding, supporting the importance of ternary complex geometry.
Client Testimonial
BOC Sciences helped us move from a broad RIPTAC hypothesis to a structured experimental program. Their integrated design, synthesis, assay planning, and SAR interpretation allowed us to understand which linker and effector choices were responsible for productive activity and which directions should be discontinued.
Project Background
An innovative drug discovery group wanted to explore a mutant intracellular protein as a selective anchor for RIPTAC research. The client had a weak binder from a fragment-to-lead campaign and needed support to improve ligand suitability, design bifunctional molecules, and establish assays capable of confirming target-dependent effector impairment. The early binder had acceptable biochemical affinity but poor cellular activity after conjugation, suggesting that linker attachment and intracellular exposure could become major bottlenecks.
Our Support
We began with binding mode analysis and protein structure modeling to compare four possible exit vectors. Two vectors were prioritized because they preserved key hinge-region contacts and projected away from the predicted protein interface. We designed 32 RIPTAC analogs across four linker families, including polar PEG linkers, lipophilic alkyl linkers, rigid piperazine-containing linkers, and mixed heteroatom linkers. During testing, several highly polar analogs showed good biochemical binding but weak cellular response, while overly lipophilic analogs produced nonspecific viability effects in both mutant-positive and mutant-low models. The most balanced series used an intermediate-length heterocyclic linker, which improved cellular activity and maintained a target-dependent response window. Follow-up competition studies using excess free target ligand reduced the functional signal, supporting a target-engagement-dependent mechanism. The client received a prioritized set of three analogs for further exploration and a clear SAR map linking linker polarity, complex formation, and cellular selectivity.
Client Testimonial
The BOC Sciences team provided a practical path for a difficult RIPTAC project. Their ability to connect structural hypotheses with synthesis, binding data, cellular exposure, and functional assays helped us identify the first meaningful chemical series for our mutant protein program.
Expands Induced Proximity Beyond Degradation
