PDC-1421 · program
PDC-1421 for Attention-deficit/hyperactivity disorder
Indications for PDC-1421: Major depressive disorder · Phase 2 Attention-deficit/hyperactivity disorder · Phase 2
PDC-1421 (ABV-1505), the same Radix Polygalae extract as ABV-1504, for adult ADHD, on the sponsor's rationale that it may raise norepinephrine levels by inhibiting reuptake. The FDA cleared the Phase 2 IND in January 2016. Part I (NCT02699086, UCSF, 2019-2020) was an open-label study in 6 adults, of whom 5 reached a 40% or greater improvement on the ADHD-RS-IV after 8 weeks. Part II (NCT05202327) was a randomized, double-blind, placebo-controlled study at UCSF and five Taiwanese sites, testing 1 or 2 capsules three times daily for 8 weeks; 69 participants started and it completed in April 2024. Results posted on ClinicalTrials.gov in May 2026 show no advantage over placebo on the primary responder endpoint: 50% responded on placebo, 39% on the low dose and 42% on the high dose. ABVC has not publicly announced Part II topline results, and its 2026 filings still list completing Part II as a goal.
Development timeline
- missedPhase 2 Part II of PDC-1421 (ABV-1505) in adult ADHD: posted results show no responder advantage over placebo (placebo 50%, low dose 39%, high dose 42%)
- Part II completed (CT.gov study completion date; primary completion 2023-12-06). Results posted 2026-05-06 show no separation from placebo on the primary responder endpoint.
- Trial (portion) completedPhase 2 Part II study of PDC-1421 in adult ADHD completed
- Randomized, double-blind, placebo-controlled Part II (NCT05202327) started at UCSF and five Taiwanese sites.
- Part I last patient visit; full clinical study report issued 2020-10-24, which the sponsor described as showing safety, tolerability and efficacy.
- Open-label Phase 2 Part I in adult ADHD (NCT02699086, UCSF) started.
Readouts
- 2026-05-06ReportedRegistry resultsmissedNCT05202327
Phase 2 Part II of PDC-1421 (ABV-1505) in adult ADHD: posted results show no responder advantage over placebo (placebo 50%, low dose 39%, high dose 42%)
Clinical trials in Attention-deficit/hyperactivity disorder
NCT05202327BLI-1008-002Phase 2Completedn=99
PDC-1421 Treatment in Adult Patients With ADHD
missedprimaryParticipants with >=40% improvement in ADHD-RS-IV from baseline up to 8 weeks (randomized, double-blind, placebo-controlled) — Responders: placebo 11/22 (50%), low dose 9/23 (39%), high dose 10/24 (42%) (No statistical analysis posted)
Neither PDC-1421 dose showed a higher responder rate than placebo; both active arms were numerically lower. Secondary: CGI score of 2 or lower in placebo 6/22, low dose 9/23, high dose 9/24. 69 participants started (registered enrollment 99). Results first posted on ClinicalTrials.gov 2026-05-06. The sponsor's filings describe an interim analysis with a clinical study report sent to the FDA but have not publicly characterized the outcome.
NCT02699086BLI-1008-001Phase 2Completedn=6
A Study of PDC-1421 Treatment in Adult Patients With Attention-Deficit Hyperactivity Disorder (ADHD)
metprimaryParticipants with >=40% improvement in ADHD-RS-IV from baseline up to 8 weeks (open-label, low dose then high dose) — 5 of 6 participants (ITT) achieved >=40% ADHD-RS-IV improvement at Week 8
Open-label, single-arm, 6-patient study at UCSF (no placebo, no statistical test). The sponsor described PDC-1421 as safe, well tolerated and efficacious in this study. Too small and uncontrolled to establish efficacy.
NCT01774045Phase 1Completedn=30
A Dose Escalation Phase I Study of PDC-1421 Capsule to Evaluate the Safety in Healthy Volunteers
metprimaryDose-limiting toxicities (physical exam, ECG, vital signs, laboratory values, C-SSRS) after single oral doses of 1, 3, 6 or 10 capsules (380-3,800 mg) — 0 dose-limiting toxicities in PDC-1421 and placebo groups on every registered primary measure
Single doses up to 3,800 mg were safe and well tolerated in 30 healthy volunteers in Taiwan, with no dose-limiting toxicities and no suicidal ideation or behavior reported.
Formulations
| Formulation | Route | Regimen | Pharmacokinetics |
|---|---|---|---|
| PDC-1421 oral capsule (380 mg Radix Polygalae extract) Capsule containing 380 mg PDC-1421 extract. Phase 1: single doses of 1, 3, 6 or 10 capsules (380-3,800 mg) after a meal. Phase 2 MDD and ADHD studies: 1 capsule (low dose, 380 mg) or 2 capsules (high dose, 760 mg) three times daily after meals; 28-day (Part I) to 42-day (MDD Part II) or 56-day (ADHD Part II) treatment periods. Placebo capsules contained corn starch. | Oral | Three times daily | — |
Mechanism of action
Mechanism as described by the sponsor: a botanical norepinephrine reuptake inhibitor. In radioligand-binding assays run in 2007, the extract inhibited the norepinephrine transporter with an IC50 of 2.102 micrograms/mL, with weaker activity at the dopamine and serotonin transporters. Because the test article is a multi-component plant extract, this is not a molecular binding constant, and no single active constituent or independent peer-reviewed confirmation of the mechanism was found.
| Target | Action | Affinity |
|---|---|---|
| NETprimarySLC6A2 | Reuptake inhibitor | —ⓘ |
← Full PDC-1421 compound page (identity, identifiers, all indications)
Sources
- ABVC BioPharma, Inc. Form 10-K for fiscal year 2025 (filed 2026-03-03) — U.S. Securities and Exchange Commission (EDGAR)
- ABVC BioPharma, Inc. Form 10-Q for the quarter ended 2026-06-30 (filed 2026-08-12) — U.S. Securities and Exchange Commission (EDGAR)
- NCT01774045 - A Dose Escalation Phase I Study of PDC-1421 Capsule to Evaluate the Safety in Healthy Volunteers (results posted) — ClinicalTrials.gov (U.S. National Library of Medicine)
- NCT02395978 (BLI-1005-002) - A Phase II Study of PDC-1421 Capsule to Evaluate the Safety and Efficacy in Patients With Major Depressive Disorder (results posted) — ClinicalTrials.gov (U.S. National Library of Medicine)
- NCT02699086 (BLI-1008-001) - A Phase II Tolerability and Efficacy Study of PDC-1421 Treatment in Adult Patients With ADHD, Part I (results posted) — ClinicalTrials.gov (U.S. National Library of Medicine)
- NCT05202327 (BLI-1008-002) - A Phase II Tolerability and Efficacy Study of PDC-1421 Treatment in Adult Patients With ADHD, Part II (results posted 2026-05-06) — ClinicalTrials.gov (U.S. National Library of Medicine)