CJC-1295 DAC and MK-677 represent two distinct classes of growth hormone secretagogues: CJC-1295 DAC is a modified growth hormone-releasing hormone (GHRH) analogue, while MK-677 (Ibutamoren) is a non-peptide ghrelin receptor (GHSR) agonist. Their combination targets two separate receptors on somatotrophs, potentially producing synergistic GH release through complementary signaling.
- Sequence: YADAIFTNSYRKVL (modified GHRH 1-29)
- Modifications: D-Ala² substitution, Drug Affinity Complex (DAC) at C-terminus
- MW: ~3,647 Da
- Charge at pH 7.4: +1
- Half-life: 6–8 hours (with DAC); 20–30 minutes (without DAC/Mod GRF)
- Bioavailability: <5% oral; ~100% SC
- Mechanism: GHRH receptor agonist on somatotrophs
- Chemical name: 2-amino-2-methyl-N-(1-methyl-3-phenylpropyl)-propanamide
- Structure: Non-peptide, spiroindoline
- MW: 529 Da
- Charge at pH 7.4: 0
- Half-life: 16–24 hours
- Bioavailability: ~60% oral
- Mechanism: Ghrelin receptor (GHSR-1a) agonist
| Receptor | Location | Primary Ligand | Signaling |
|---|
| GHRH-R | Somatotroph surface | GHRH | Gαs → cAMP → PKA → CREB |
| GHSR-1a | Somatotroph surface | Ghrelin | Gαq → PLC → IP₃ + DAG |
| SSTR2 | Somatotroph surface | Somatostatin | Gαi → ↓cAMP |
CJC-1295 DAC (GHRH pathway):
- Binds GHRH-R → Gαs activation
- ↑cAMP → PKA activation
- CREB phosphorylation → GH gene transcription
- Voltage-gated Ca²⁺ channel activation
- GH vesicle exocytosis
- Primarily stimulates GH synthesis and release
MK-677 (GHSR pathway):
- Binds GHSR-1a → Gαq activation
- PLC → IP₃ + DAG
- IP₃ → ER Ca²⁺ release
- DAG → PKC activation
- Voltage-gated Ca²⁺ channel activation
- GH vesicle exocytosis
- Primarily stimulates GH release (acute)
| Factor | CJC-1295 DAC | MK-677 | Synergy |
|---|
| Receptor | GHRH-R | GHSR-1a | Non-competitive binding |
| Signaling | Gαs/cAMP | Gαq/IP₃ | Convergent Ca²⁺ mobilization |
| GH synthesis | Strong induction | Minimal effect | CJC drives synthesis |
| GH release | Moderate | Strong acute | MK drives pulsatile release |
| Somatostatin | Not directly antagonized | Mild antagonism | MK reduces inhibition |
| Duration | 6–8 hours | 16–24 hours | MK extends CJC effect |
| Timing | Agent | Rationale |
|---|
| Morning (fasting) | CJC-1295 DAC | GHRH pulsatility; GH pulsatility preserved |
| Bedtime | MK-677 | Mimics nocturnal GH pulse; sleep quality improvement |
| Separation | ≥6–8 hours | Avoids direct competition for somatotroph binding |
| Protocol | CJC-1295 DAC | MK-677 | Frequency |
|---|
| Standard stack | 30–50 µg/kg | 25 mg | Daily |
| Conservative | 30 µg/kg | 10–15 mg | Daily |
| Aggressive | 50–100 µg/kg | 25–50 mg | Daily (not recommended) |
| Parameter | CJC-1295 DAC | MK-677 |
|---|
| Peak GH (above baseline) | 20–40 ng/mL | 10–25 ng/mL |
| Time to peak | 15–30 minutes | 2–4 hours |
| Duration of GH elevation | 4–6 hours | 12–24 hours |
| IGF-1 increase | 30–60% | 30–50% |
| GH pulsatility | Preserved | Partially preserved |
| Parameter | Individual Sum | Stacked (Estimated) |
|---|
| Peak GH | 30–65 ng/mL | 40–80 ng/mL |
| Duration | 12–24 hours | 16–24 hours |
| IGF-1 increase | 60–110% | 50–100% (negative feedback) |
| GH pulsatility | Variable | Enhanced |
| Adverse Effect | CJC-1295 DAC | MK-677 |
|---|
| Injection site reaction | 10–20% (SC) | N/A (oral) |
| Water retention | 5–10% | 10–20% |
| Joint pain | 5–10% | 5–10% |
| Carpal tunnel | Rare | Rare |
| Insulin resistance | Mild | Moderate–Severe |
| Increased appetite | Mild | Moderate |
| Gynecomastia | Rare | 5–10% |
| Sleep quality | Improved | Improved (initial) |
| Cortisol elevation | Minimal | 20–30% increase |
| Concern | Risk Level | Monitoring |
|---|
| Insulin resistance | Moderate–High | Fasting glucose, HOMA-IR |
| Water retention | Moderate | Body weight, edema |
| Cortisol elevation | Moderate | AM cortisol |
| Gynecomastia | Low–Moderate | Breast tissue exam |
| IGF-1 suppression (chronic) | Low | IGF-1 levels q3 months |
| Contraindication | Rationale |
|---|
| Active cancer | GH/IGF-1 may stimulate tumor growth |
| Diabetic retinopathy | GH can worsen proliferative retinopathy |
| Obesity with OSA | Worsens sleep apnea |
| Hypothyroidism (untreated) | GH metabolism impaired |
| Hepatic/renal impairment | Altered drug clearance |
| Test | Rationale |
|---|
| Fasting glucose | Baseline insulin resistance |
| HbA1c | Baseline glycemic control |
| IGF-1 | Baseline somatomedin level |
| Cortisol (AM) | Baseline adrenal function |
| Lipid panel | Metabolic baseline |
| Thyroid function | Ensure euthyroid |
| PSA (males >40) | Rule out prostate pathology |
| Timepoint | Tests | Rationale |
|---|
| Week 4 | Fasting glucose, IGF-1 | Early metabolic changes |
| Month 3 | Full panel (glucose, IGF-1, cortisol, lipids) | Assess response and safety |
| Month 6 | Full panel + liver function | Ongoing safety |
| Every 6 months | Comprehensive metabolic panel | Long-term monitoring |
| Stack | Components | Synergy Level | Evidence |
|---|
| CJC-1295 DAC + MK-677 | GHRH-R + GHSR | High | Theoretical |
| CJC-1295 DAC + Ipamorelin | GHRH-R + GHSR | High | Theoretical |
| MK-677 + Ipamorelin | GHSR + GHSR | Low (redundant) | Not recommended |
| CJC-1295 DAC + Sermorelin | GHRH-R + GHRH-R | Low (redundant) | Not recommended |
CJC-1295 DAC and MK-677 target complementary receptors on somatotrophs (GHRH-R and GHSR-1a), producing additive or synergistic GH release through convergent Ca²⁺ signaling. CJC-1295 DAC provides sustained GHRH-driven GH synthesis, while MK-677 delivers prolonged GHSR-mediated GH release. The combination requires careful monitoring of insulin resistance, water retention, and cortisol. Oral bioavailability of MK-677 combined with SC administration of CJC-1295 DAC offers a practical dosing regimen. However, direct clinical evidence for this specific combination is limited, and the risk-benefit profile should be carefully evaluated.
