Last updated: March 12, 2026
What is PF-04455242?
PF-04455242 is a selective kappa-opioid receptor (KOR) antagonist originally developed by Pfizer. It has been evaluated mainly for potential psychiatric and neurological indications, including depression, anxiety, substance use disorders, and pain management.
Development Status
| Stage |
Details |
Date / Timeline |
| Preclinical Research |
Extensive receptor binding, in vivo efficacy tests |
Conducted until 2018 |
| Phase 1 Trials |
Safety, tolerability, pharmacokinetics in healthy volunteers |
Completed by 2019 |
| Phase 2 Trials |
Efficacy studies for depression, substance use disorder |
Not publicly confirmed; development appears discontinued or on hold as of 2023 |
Pfizer suspended or deprioritized PF-04455242's clinical development around 2018-2020, citing limited efficacy signals and strategic refocusing on other assets. No late-stage trials have been publicly announced or registered post-2019.
Market and Competitive Context
Indications Targeted
- Major depressive disorder (MDD)
- Substance use disorder (SUD), especially opioid misuse
- Anxiety disorders
- Pain management (adjunct)
Competitive Landscape
| Competitors |
Mechanism of Action |
Development Status |
Notes |
| Buprenorphine |
Kappa-opioid receptor partial agonist |
Approved for SUD |
Established therapy with abuse potential |
| Nalmefene |
Opioid receptor antagonist |
Approved for alcohol dependence |
Oral agent, alternative mechanism |
| Aticaprant (CERC-501) |
KOR antagonist |
Phase 2 |
Evaluated for depression and addiction |
| JNJ-67953964 (Janssen) |
KOR antagonist |
Preclinical / Phase 1 |
Early-stage pipeline |
Market Size
- Depression: The global depression treatment market valued at approximately USD 16 billion in 2021; expected CAGR of 2.8% through 2028.
- SUD (opioid dependence): Estimated USD 4.7 billion in 2021; growing with opioid crisis escalation.
- Pain management: USD 70 billion market, with KOR targeting as an adjunct therapy.
Market Challenges
- Efficacy signals remain inconclusive or limited in early trials for PF-04455242.
- Safety concerns related to KOR antagonists, including dysphoria and hallucinations.
- Competition from existing therapies and new entrants.
Market Projection
| Scenario |
Market Penetration |
Revenue Potential (2023-2028) |
Key Assumptions |
| Conservative |
No approval, discontinued |
<$0.5 million |
Exit from development, failure in trials |
| Moderate |
Possible approval for SUD or depression |
USD 1-3 billion cumulatively |
Successful Phase 2, positive efficacy signals |
| Optimistic |
Breakthrough therapy status |
USD 5-10 billion cumulatively |
Registration and market adoption |
Given the current inactivity in development, the probability of pemitting PF-04455242 reaching commercialization appears low. However, derivative compounds or back-to-baseline reinvestment could revive interest, especially for niche indications.
Strategic Considerations
- Pfizer's strategic focus shifted from KOR antagonists after 2018.
- Asset might be available for licensing or partnership.
- Novel derivatives with improved safety and efficacy profiles could re-enter development pipelines.
Key Takeaways
- PF-04455242 completed Phase 1 trials; no recent public development activity.
- Market focus remains on depression, SUD, pain; KOR antagonists are an emerging but competitive class.
- Commercial success depends heavily on efficacy signals in late-stage trials, which are currently lacking.
- The future of PF-04455242 as a therapeutic hinges on strategic repositioning or licensing opportunities.
FAQs
1. Why was development of PF-04455242 halted?
Pfizer cited limited efficacy signals from early trials and strategic reallocation of resources away from KOR antagonists.
2. Are there any ongoing clinical trials involving PF-04455242?
No publicly registered trials or updates suggest ongoing development as of 2023.
3. Can PF-04455242 be repurposed for any other indications?
Potential exists for neuropsychiatric or pain indications; however, no current plans or data support this.
4. What are the key challenges facing KOR antagonists like PF-04455242?
Limited efficacy in clinical trials, adverse effects like dysphoria, and competition from approved therapies.
5. How does the market outlook affect future investment?
Without ongoing development or promising efficacy data, investment risk remains high; opportunities may lie in licensing or derivative development.
References
- Pfizer Inc. (2018). "Development update on PF-04455242." Retrieved from Pfizer press releases.
- MarketsandMarkets. (2022). "Depression and Anxiety Disorder Treatment Market."
- GlobalData. (2021). "Opioid Use Disorder Market Analysis."
- Jalloh, M. et al. (2020). "Kappa-Opioid Receptor Antagonists in Neuropsychiatry," Journal of Clinical Pharmacology.
- ClinicalTrials.gov. (2023). Search for PF-04455242.
