# Sierra Oncology

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

## TL;DR

A former California company that developed momelotinib, a pill for myelofibrosis, a bone marrow cancer, especially for patients with anaemia. GSK bought it in 2022.

## Summary

Sierra Oncology was a California-based biopharmaceutical company focused on targeted therapies for rare forms of cancer, listed on Nasdaq as SRRA. Its lead asset was momelotinib, which GSK describes as inhibiting ACVR1/ALK2, JAK1 and JAK2, developed for myelofibrosis patients with anaemia; in January 2022 Sierra announced that the Phase 3 MOMENTUM trial (NCT04173494) met its primary and key secondary endpoints. GSK agreed on 13 April 2022 to acquire Sierra for $55 per share in cash, about $1.9 billion in equity value, and announced on 1 July 2022 that the acquisition was complete, after Sierra shareholders approved it on 29 June 2022. SEC records list ProNAi Therapeutics as the company's earlier name until January 2017.

## Fields

- Kind: Company
- Last checked: 2026-11-04
- Also known as: Sierra Oncology, Inc.; Sierra Oncology LLC; ProNAi Therapeutics
- HQ: San Mateo, CA
- Type: biotech

## Notes

- The company website is gone; the acquirer's releases are the sources.
- Founding year not read from a primary source.
- Many earlier momelotinib, SRA737 and PNT2258 trials now list 'Sierra Oncology LLC - a GSK company' as sponsor on ClinicalTrials.gov; only MOMENTUM is a trial record in OnCo.

## Sources

- GSK press release: agreement to acquire Sierra Oncology, 13 April 2022: https://www.gsk.com/en-gb/media/press-releases/gsk-reaches-agreement-to-acquire-late-stage-biopharmaceutical-company-sierra-oncology-for-19bn/
- GSK completes acquisition of Sierra Oncology (SEC Form 6-K, 1 July 2022): https://www.sec.gov/Archives/edgar/data/1131399/000165495422009090/a0772r.htm
- SEC EDGAR filings: https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001290149
- RA Capital portfolio entry: https://www.racap.com/portfolio/sierra-oncology

## Connected records

- cancers: [Primary myelofibrosis](https://onco.cc/cancers/primary-myelofibrosis/)
- fronts: [Targeted Therapy](https://onco.cc/fronts/targeted-therapy/)
- technologies: [Small-molecule kinase inhibitors](https://onco.cc/technologies/kinase-inhibitors/)
- drugs: [Momelotinib](https://onco.cc/drugs/momelotinib/)
- trials: [MOMENTUM](https://onco.cc/trials/momentum/)
- companies: [GSK](https://onco.cc/companies/gsk/), [RA Capital Management](https://onco.cc/companies/ra-capital/)

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JSON: https://onco.cc/api/v1/entities/sierra-oncology.json