# Iniparib

Source: https://onco.cc/drugs/iniparib/  
OnCo record `iniparib` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Billed as the first PARP inhibitor for triple-negative breast cancer, it failed its phase 3 in 2011. It turned out not to inhibit PARP at all.

## Summary

A randomised phase 2 (O'Shaughnessy, NEJM 2011) in metastatic TNBC showed improved response, PFS, and OS when iniparib was added to gemcitabine-carboplatin. The phase 3 (n=519) missed both co-primary endpoints. Subsequent biochemistry showed iniparib does not trap or inhibit PARP1/2 at clinically relevant concentrations; it acts as a non-specific thiol-reactive compound. Sanofi (which had bought BiPar for up to $500M) discontinued it after a negative phase 3 in squamous NSCLC (2013).

Lesson: mechanism claims should be verified before a class label is attached; the true PARP inhibitors (olaparib, talazoparib) later succeeded in BRCA-mutant breast cancer.

## Fields

- Kind: Treatment
- Status: negative
- Last checked: 2026-09-06
- Tags: failure; lesson:wrong-drug
- Code: BSI-201, SAR240550
- Modality: Small molecule (claimed PARP inhibitor)
- Mechanism: Originally described as a PARP1 inhibitor; later shown to be a non-selective cysteine-modifying agent without PARP inhibition.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Iniparib
- Iniparib is not a PARP inhibitor (Clin Cancer Res 2012): https://aacrjournals.org/clincancerres/article/18/2/510/76892/A-Deep-Look-at-the-PARP-Inhibitor-Iniparib

## Connected records

- cancers: [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- technologies: [PARP inhibitors](https://onco.cc/technologies/parp-inhibitor/)
- targets: [PARP](https://onco.cc/targets/parp/)
- drugs: [Olaparib](https://onco.cc/drugs/olaparib/), [Talazoparib](https://onco.cc/drugs/talazoparib/)
- companies: [Sanofi](https://onco.cc/companies/sanofi/)
- trials: [A Phase 3, Multi-Center Study of Gemcitabine/Carboplatin, With or Without BSI-201, in Patients With ER-, PR-, and Her2-Negative Metastatic Breast Cancer](https://onco.cc/trials/nct00938652/), [Study of SAR240550 (BSI-201) in Combination With Gemcitabine/Carboplatin, in Patients With Metastatic Triple Negative Breast Cancer](https://onco.cc/trials/nct01045304/), [Two Regimens of SAR240550/Weekly Paclitaxel and Paclitaxel Alone as Neoadjuvant Therapy in Triple Negative Breast Cancer Patients](https://onco.cc/trials/nct01204125/)
- bottlenecks: [Failures are hidden](https://onco.cc/bottlenecks/b-negative-results/)

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