Bitopertin
An investigational treatment for Erythropoietic Protoporphyria.
The same compound appears under different names depending on the context. Here is how to identify Bitopertin wherever you encounter it, plus the key facts at a glance.
- Generic name
- Bitopertin
- Development code
- DISC-1459
- Drug class
- Glycine transporter 1 inhibitor
- Manufacturer
- Disc Medicine
- How it's taken
- Oral tablet once daily (60 mg in the expanded access program)
A once-daily pill from Disc Medicine that lowers the protoporphyrin that causes EPP, rather than darkening the skin. The FDA declined its accelerated approval application on February 13, 2026 because the early trials did not tie the protoporphyrin drop to more pain-free sunlight; the Phase 3 APOLLO trial, designed to answer that, finished in September 2026 with topline results scheduled for October 19, 2026.
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Where Bitopertin fits
Bitopertin is the first EPP drug to aim at the cause, the excess protoporphyrin, which is also what drives the liver complications. If the APOLLO trial succeeds and the FDA approves it, it would sit beside Scenesse and dersimelagon as a different kind of option. US patients aged 12 and up who lack satisfactory alternatives can ask about Disc's expanded access program now.
How Bitopertin works
Heme, the iron-carrying part of hemoglobin, is built in developing red blood cells from glycine and a second small molecule. GlyT1 is the transporter that pulls glycine into those cells[3]. Bitopertin blocks GlyT1, so less glycine enters, the heme pathway runs more slowly and less protoporphyrin IX is made, which is the chemical that reacts with light in EPP and XLP[3].
Because it lowers protoporphyrin in blood and plasma rather than adding pigment to the skin, Disc describes it as potentially the first disease-modifying therapy for the protoporphyrias[3]. The FDA's letter accepted that the biology is plausible and that the drug lowers whole blood metal-free protoporphyrin IX; what it asked for was proof that the drop translates into more time in sunlight without pain[2].
Mechanism: Oral inhibitor of glycine transporter 1 (GlyT1) on developing red blood cells, which limits the glycine supply for heme synthesis and lowers production of protoporphyrin IX
Side effects and safety
There is no FDA label, and Disc has not published a pooled safety table in a press release. The FDA's complete response letter did not raise safety concerns; its reasons were about proof of clinical benefit[2]. Bitopertin was first developed by Roche at higher doses for schizophrenia, so a safety database exists from that program; Disc licensed the drug from Roche in May 2021[3].
The HELIOS extension study's primary measures are adverse events, vital signs, physical exams, laboratory results and 2 mental health screens, the PHQ-8 for depression and the Columbia Suicide Severity Rating Scale[9]. A safety summary from APOLLO is expected with the topline results.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Bitopertin
A tablet taken by mouth once a day. The expanded access program and the Phase 3 trial's higher arm use 60 mg once daily; the earlier AURORA trial compared 20 mg and 60 mg with placebo[10][2]. The expanded access program is open in the US to people with EPP or XLP aged 12 and up who lack satisfactory treatment options and meet other criteria; requests go through a treating doctor to bitopertinEAP@discmedicine.com[5].
Access and eligibility
The expanded access program is for people in the US with EPP or XLP aged 12 and up who have no satisfactory treatment options and meet additional criteria set by Disc. APOLLO and HELIOS enrolled people aged 12 and up with EPP or XLP; HELIOS is open by invitation to people who completed an earlier bitopertin trial.
Source: Disc Medicine expanded access announcement
Access program details are provided for informational purposes and may vary based on insurance coverage, geographic location, and individual circumstances. Confirm current eligibility directly with the manufacturer or your specialty pharmacy.
How EPP and XLP treatments compare
Scenesse is the only FDA-approved treatment for erythropoietic protoporphyria, and it is approved for adults. Behind it are 3 oral drugs at different stages: dersimelagon is under FDA review, bitopertin received a complete response letter and finished its Phase 3 trial, and PORT-77 is recruiting for a Phase 2b/3 trial. Scenesse and dersimelagon work on skin pigment; bitopertin and PORT-77 try to lower protoporphyrin itself. None has been compared head to head.
Erythropoietic Protoporphyria has 1 FDA-approved treatment: Scenesse (afamelanotide, approved 2019). Also compared, not FDA-approved for erythropoietic protoporphyria: Dersimelagon (MT-7117) (dersimelagon, Under FDA priority review, decision by end of February 2027); Bitopertin (DISC-1459) (bitopertin, Complete response letter February 13, 2026; Phase 3 APOLLO topline due October 19, 2026); PORT-77 (PORT-77, Phase 2b/3 recruiting; not yet reviewed by the FDA). Scenesse is typically used as adults with a history of phototoxic reactions from epp.
| Drug | How it works | How it’s given | How often | Where you get it | Who it is for | FDA status |
|---|---|---|---|---|---|---|
Scenesse afamelanotide | MC1R agonist: a peptide that switches on eumelanin production so the skin absorbs light before it reaches protoporphyrin | Dissolving 16 mg implant placed under the skin above the hip | Every 2 months | Clinuvel-accredited EPP Specialty Center (about 120 in North America) | Adults with a history of phototoxic reactions from EPP | 2019 |
Dersimelagon (MT-7117) dersimelagon | MC1R agonist: a small molecule with the same pigment target as Scenesse | Oral tablet | Once daily (200 mg in Phase 3) | Home, if approved | Studied in people aged 12 to under 75 with EPP or XLP | Under FDA priority review, decision by end of February 2027 |
Bitopertin (DISC-1459) bitopertin You are here | GlyT1 inhibitor: slows heme production in developing red cells so less protoporphyrin is made | Oral tablet | Once daily (60 mg in Phase 3 and expanded access) | Home; US expanded access program for ages 12 and up without satisfactory options | Studied in people aged 12 and up with EPP or XLP | Complete response letter February 13, 2026; Phase 3 APOLLO topline due October 19, 2026 |
PORT-77 PORT-77 | ABCG2 inhibitor: blocks the pump that moves protoporphyrin out of red cells into plasma | Oral tablet | Once or twice daily (dose being chosen in Phase 2b) | Clinical trial sites in the US | Recruiting people aged 12 and up with EPP or XLP for PATHWAY | Phase 2b/3 recruiting; not yet reviewed by the FDA |
Only Scenesse is FDA approved. Dersimelagon, bitopertin and PORT-77 are investigational and their results come from company announcements and trial registrations, not FDA labels; the FDA has not reviewed PORT-77 and declined bitopertin's first application. Trial results for different drugs measured different things over different periods and cannot be compared directly. Talk with a porphyria specialist about what fits your age, your liver and iron tests and your access to an accredited center.
Clinical trial results
The first application rested on 2 Phase 2 trials[2]. AURORA (NCT05308472, Trial 201) randomized adults with EPP at 9 US sites to bitopertin 20 mg, 60 mg or placebo for 120 days; 60 mg beat placebo on the primary endpoint, percent change in whole blood metal-free protoporphyrin IX at day 121 (p<0.001), with a reduction the FDA described as about 40% from baseline[2].
BEACON (Trial 202), an open-label trial at 2 Australian sites in people aged 12 and up with EPP or XLP, found 60 mg lowered the biomarker more than 20 mg at day 169 (p=0.018)[2]. Neither trial showed an association between the biomarker change and the sunlight exposure endpoints as measured, which is why the FDA declined accelerated approval[2][3].
APOLLO (NCT06910358), the Phase 3 trial, randomized 183 people aged 12 and up with EPP or XLP to bitopertin or placebo once daily for 24 weeks at sites in the US, Canada, Europe and Australia[8][4]. Its co-primary endpoints are the average monthly time in sunlight without pain between 10 AM and 6 PM in the last month of treatment, and the percent change in whole blood metal-free protoporphyrin IX at 6 months[4].
Enrollment finished in March 2026, the registry lists primary completion on September 8, 2026, and Disc scheduled a webcast on October 19, 2026 at 8 AM ET to present topline results[6][8][1]. HELIOS (NCT05883748) is the open-label extension, with 230 planned participants, running to June 2028[9].
Main registered trial: NCT07603401 on ClinicalTrials.gov. Check it for the current status, sites and contacts before asking about enrollment.
Development history
Roche developed bitopertin for schizophrenia, where it did not succeed, and Disc Medicine licensed global rights in May 2021 to repurpose it for the protoporphyrias[3]. Disc submitted an NDA in 2025 under the accelerated approval pathway using the protoporphyrin biomarker as a surrogate endpoint; the FDA accepted it with priority review and awarded it a Commissioner's National Priority Voucher, a pilot meant to shorten review to 1 to 2 months[7].
On February 13, 2026 the FDA issued a complete response letter: it agreed the drug significantly lowers the biomarker but said the trials did not show that the change predicts more pain-free sunlight, and asked for evidence from an adequate and well-controlled trial based on clinical endpoints, naming APOLLO as the study that could support traditional approval[2][3].
Disc completed APOLLO enrollment in March 2026, expanded to 183 participants because of demand[6]. It launched an expanded access program on June 1, 2026[5]. On June 9, 2026 it reported a Type A meeting at which it aligned with the FDA that a successful APOLLO can serve as the basis for a CRL response and could support traditional approval, with the response expected by the end of 2026 and an FDA decision expected by mid-2027[4].
On October 18, 2026 Disc announced the APOLLO topline webcast for the next morning[1]. The results were not public when this page was written.
Explore Erythropoietic Protoporphyria trials
Other Erythropoietic Protoporphyria treatments
Bitopertin and PORT-77 are the 2 EPP drugs that try to lower protoporphyrin itself, which could matter for the liver as well as the skin; Scenesse and dersimelagon act on skin pigment. Which approach helps more, and whether they could be combined, has not been tested.
Common questions about Bitopertin
▸What is Bitopertin?
A once-daily pill from Disc Medicine that lowers the protoporphyrin that causes EPP, rather than darkening the skin. The FDA declined its accelerated approval application on February 13, 2026 because the early trials did not tie the protoporphyrin drop to more pain-free sunlight; the Phase 3 APOLLO trial, designed to answer that, finished in September 2026 with topline results scheduled for October 19, 2026.
▸How does Bitopertin work?
Heme, the iron-carrying part of hemoglobin, is built in developing red blood cells from glycine and a second small molecule. GlyT1 is the transporter that pulls glycine into those cells[3]. Bitopertin blocks GlyT1, so less glycine enters, the heme pathway runs more slowly and less protoporphyrin IX is made, which is the chemical that reacts with light in EPP and XLP[3]. Because it lowers protoporphyrin in blood and plasma rather than adding pigment to the skin, Disc describes it as potentially the first disease-modifying therapy for the protoporphyrias[3]. The FDA's letter accepted that the biology is plausible and that the drug lowers whole blood metal-free protoporphyrin IX; what it asked for was proof that the drop translates into more time in sunlight without pain[2].
▸What are the side effects of Bitopertin?
There is no FDA label, and Disc has not published a pooled safety table in a press release. The FDA's complete response letter did not raise safety concerns; its reasons were about proof of clinical benefit[2]. Bitopertin was first developed by Roche at higher doses for schizophrenia, so a safety database exists from that program; Disc licensed the drug from Roche in May 2021[3]. The HELIOS extension study's primary measures are adverse events, vital signs, physical exams, laboratory results and 2 mental health screens, the PHQ-8 for depression and the Columbia Suicide Severity Rating Scale[9]. A safety summary from APOLLO is expected with the topline results.
▸How is Bitopertin taken?
A tablet taken by mouth once a day. The expanded access program and the Phase 3 trial's higher arm use 60 mg once daily; the earlier AURORA trial compared 20 mg and 60 mg with placebo[10][2]. The expanded access program is open in the US to people with EPP or XLP aged 12 and up who lack satisfactory treatment options and meet other criteria; requests go through a treating doctor to bitopertinEAP@discmedicine.com[5].
▸Is Bitopertin FDA approved?
Bitopertin is currently in crl clinical trials for Erythropoietic Protoporphyria. It has not yet received FDA approval.
▸Why did the FDA reject bitopertin for EPP?
The FDA agreed the drug lowers protoporphyrin but said the trials did not show that the drop leads to more pain-free time in sunlight.
Date: complete response letter issued February 13, 2026.
FDA's words: the trials "did not show evidence of association between percent change in whole blood metal-free PPIX and sunlight-exposure based endpoints."
What it asked for: results from an adequate and well-controlled trial based on clinical endpoints, which is what APOLLO measures.
Source: FDA complete response letter, NDA 220707; Disc Medicine, February 13, 2026
▸When will bitopertin's APOLLO results come out?
Disc Medicine scheduled a webcast for Monday, October 19, 2026 at 8 AM Eastern to present the topline results.
Trial: 183 people aged 12 and up with EPP or XLP, 24 weeks, placebo controlled.
What counts: time in sunlight without pain in the last month, and the change in blood protoporphyrin.
Source: Disc Medicine, October 18, 2026
▸When could the FDA approve bitopertin?
Disc Medicine expects an FDA decision by mid-2027 if APOLLO succeeds.
Steps: submit a response to the complete response letter by the end of 2026, then the FDA reviews it.
FDA position: at a Type A meeting the FDA agreed a successful APOLLO can serve as the basis for the response and could support traditional approval.
Source: Disc Medicine, June 9, 2026
▸Can I get bitopertin before it is approved?
Possibly, through Disc Medicine's US expanded access program.
Who: people with EPP or XLP aged 12 and up who lack satisfactory treatment options and meet other criteria.
Dose: 60 mg once a day.
How: your doctor contacts bitopertinEAP@discmedicine.com; the program is listed as NCT07603401.
Source: Disc Medicine, June 1, 2026; ClinicalTrials.gov
▸How is bitopertin different from Scenesse?
Bitopertin lowers the protoporphyrin that causes EPP; Scenesse adds pigment to the skin so light does less harm.
Form: a daily pill against an implant every 2 months.
Ages: bitopertin was studied from age 12; Scenesse is approved for adults.
Status: Scenesse is FDA approved; bitopertin is not approved anywhere.
Source: Disc Medicine; Scenesse prescribing information
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- Disc Medicine · 2026-10-18. Disc Medicine to Host Corporate Webcast to Discuss Topline Results from the APOLLO Phase 3 Trial of Bitopertin in Erythropoietic Protoporphyria (EPP). https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-host-corporate-webcast-discuss-topline-results
- FDA Center for Drug Evaluation and Research via openFDA · 2026-02-13. Complete Response, NDA 220707, bitopertin oral tablets (openFDA CRL database). https://api.fda.gov/transparency/crl.json?search=bitopertin
- Disc Medicine · 2026-02-13. Disc Medicine Receives Complete Response Letter from FDA for Bitopertin for the Treatment of EPP. https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-receives-complete-response-letter-fda-bitopertin
- Disc Medicine · 2026-06-09. Disc Medicine Provides Update from FDA Type A Meeting for Bitopertin in Erythropoietic Protoporphyria. https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-provides-update-fda-type-meeting-bitopertin
- Disc Medicine · 2026-06-01. Disc Medicine Launches Expanded Access Program for Bitopertin for EPP Patients. https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-launches-expanded-access-program-bitopertin-epp
- Disc Medicine · 2026-03-26. Disc Medicine Announces Completion of Enrollment of Phase 3 APOLLO Trial of Bitopertin in Erythropoietic Protoporphyria. https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-announces-completion-enrollment-phase-3-apollo
- Disc Medicine · 2026-01-12. Disc Medicine Highlights Recent Achievements and Key Business Objectives and Milestones for 2026. https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-highlights-recent-achievements-and-key-business
- ClinicalTrials.gov · 2026-10-09. Study of Bitopertin in Participants With EPP or XLP (APOLLO). https://clinicaltrials.gov/study/NCT06910358
- ClinicalTrials.gov · 2026-10-09. HELIOS: Open-Label, Long-Term Extension Study of DISC-1459 (Bitopertin) in Participants With EPP or XLP. https://clinicaltrials.gov/study/NCT05883748
- ClinicalTrials.gov · 2026-10-06. Expanded Access Program of Bitopertin For Participants With EPP or XLP. https://clinicaltrials.gov/study/NCT07603401