TEMPO Program — Primary Endpoints Summary
Efficacy + Unprecedented ICD Safety Profile
−9.1 pts
MDS-UPDRS II+III (TEMPO-2)
vs placebo −1.2 pts | P < .001
+1.10 hr
Good ON-Time (TEMPO-3)
vs placebo | P < .001
1.2%
ICD Incidence (All TEMPO)
vs D2/D3 agonists: 17–28%
~1%
Sleep Attacks (NS vs placebo)
vs D2/D3: 1–9%
Pharmacology — Receptor Binding Profile
D1/D5 Selective: Ki Values and Intrinsic Activity
| Receptor |
Ki (nM) |
Functional Activity |
EC50 (nM) |
| D1 |
9 |
Partial agonist (65% intrinsic) |
19 |
| D5 |
13 |
Partial agonist (81% intrinsic) |
17 |
| D2 |
>6,720 |
Negligible |
— |
| D3 |
5,240 |
Negligible |
— |
| D4 |
4,870 |
Negligible |
— |
Selectivity: D1 vs D2 >700-fold | D1 vs D3 >580-fold | D5 vs D3 >400-fold
Pharmacokinetics
24-Hour Half-Life Supports Once-Daily Dosing
Mechanism — Basal Ganglia Motor Circuit
D1 vs D2 Pathway: Motor Circuit Dysfunction in PD
Direct Pathway (D1) — "GO" Signal
SNc Dopamine
→
D1 MSNs (Striatum)
→
GPi/SNr
→
Thalamus
→
Cortex → Movement
In PD: Dopamine loss → ↓D1 activation → ↓direct pathway → ↑GPi output → Thalamic suppression → Bradykinesia
Indirect Pathway (D2) — "STOP" Signal
SNc Dopamine
→
D2 MSNs (Striatum)
→
GPe
→
STN
→
GPi
→
Thalamus
In PD: Dopamine loss → ↓D2 activation → ↑indirect pathway → ↑GPi output → Thalamic suppression → Bradykinesia
Critical Differentiator: ICD Mechanism
D2/D3 agonists (Pramipexole, Ropinirole): Stimulate D3 receptors in nucleus accumbens (VTA-NAc mesolimbic pathway) → Excessive reward signaling → ICD (pathological gambling, compulsive shopping, binge eating, hypersexuality) in 17–28% of patients.
Tavapadon: D1/D5 selective, negligible D3 affinity (Ki >5,000 nM) → No mesolimbic activation → ICD rate ~1% across all TEMPO trials.
TEMPO Clinical Development Program
Phase 3 Trials: Monotherapy + Adjunctive
TEMPO-1
Monotherapy, Fixed dose
n=529 | 27 weeks
MDS-UPDRS II+III: −9.7 to −10.2 pts ✓
ICD: 0%
TEMPO-2
Monotherapy, Flexible 5–15mg
n=304 | 27 weeks
MDS-UPDRS II+III: −9.1 pts ✓
ICD: 1.3%
TEMPO-3
Adjunctive to Levodopa
n=507 | 27 weeks
Good ON-time: +1.1 hr ✓
ICD: 1.2%
Safety — ICD Comparison
Tavapadon vs D2/D3 Agonists: Paradigm Shift in Safety
| Adverse Event |
Tavapadon (TEMPO) |
D2/D3 Agonists (Historical) |
| Impulse Control Disorders |
1.2–1.3% |
17–28% |
| Sleep Attacks |
~1% (NS vs placebo) |
1–9% |
| Somnolence |
1–3% |
5–15% |
| Hallucinations |
4–6% |
5–10% |
| Dyskinesia |
1–2% |
2–5% |
| Nausea |
10–18% |
15–25% |
Bottom Line
Comparable motor efficacy + 20× lower ICD rate + comparable motor efficacy = potential paradigm shift in dopamine agonist selection
Clinical Comparison
vs Current Adjunctive Therapies for Motor Fluctuations
| Therapy |
Mechanism |
ON-time |
ICD Risk |
Dosing |
| Tavapadon |
D1/D5 partial agonist |
↑↑ |
~1% |
QD |
| Pramipexole |
D2/D3 full agonist |
↑ |
17–28% |
TID/QD |
| Ropinirole |
D2/D3 partial agonist |
↑ |
12–20% |
TID/QD |
| Opicapone (COMT-I) |
Extend levodopa |
↑ |
Minimal |
QD |
| Amantadine (ER) |
NMDA antagonist |
Dyskinesia ↓ |
Minimal |
QD |
Clinical Utility
Ideal Candidate Selection
✓ Tavapadon Preferred
• Treatment-naïve early PD
• ICD risk factors (history, family Hx)
• Sleep disorders on D2/D3 agonists
• Geriatric patients (start low)
• Cognitive vulnerability (MCI, >75y)
• Autonomic dysfunction (OH)
• Pill burden concerns
• Once-daily dosing preference
✗ Alternatives Preferred
• Primary dyskinesia (amantadine)
• Advanced PD (LCIG, apomorphine, DBS)
• Active ICD (avoid all agonists)
• Failed/inadequate tavapadon
• Specific formulary constraints
• Cost/access limitations
Take-Home Points for Practice
- First D1/D5-selective agonist — mechanistically distinct from D2/D3 agonists
- Primary endpoints met: TEMPO-1/2 (−9 pts MDS-UPDRS), TEMPO-3 (+1.1 hr good ON-time)
- ICD rate ~1% vs 17–28% with D2/D3 agonists — the critical differentiator
- Sleep attacks: Indistinguishable from placebo (~1%)
- Once-daily dosing (5–15 mg) — flexible titration
- FDA NDA submitted Sept 2025 — potential approval 2026–2027
- Mechanism: D1/D5 selectivity avoids mesolimbic D3 circuits → ICD protection
- Long-term data: 58-week TEMPO-4 confirms sustained benefit and continued low ICD rate