Apitegromab: Dosing Protocols
Dosing guidelines, reconstitution, and administration information
๐TL;DR
- โข4 dosing protocols documented
- โขReconstitution instructions included
- โขStorage: As a monoclonal antibody, apitegromab requires refrigerated storage (2-8 degrees C) and protection from light. It must not be frozen. Storage and handling are managed by clinical trial sites per sponsor protocols.
Protocol Quick-Reference
Motor function improvement in spinal muscular atrophy (SMA)
Dosing
Amount
10-20 mg/kg
Frequency
Every 4 weeks (Q4W)
Duration
12 months (pivotal study)
Administration
Route
IVTiming
Administered as IV infusion at clinical sites under medical supervision. Background SMN-targeted therapy (nusinersen or risdiplam) required in all patients.
Cycle
Duration
12 months (extendable based on response)
Repeatable
Yes
โ๏ธ Suggested Bloodwork (4 tests)
CBC with differential
When: Baseline
Why: Baseline blood cell counts
CMP (Comprehensive Metabolic Panel)
When: Baseline
Why: Baseline liver and kidney function
Anti-drug antibody testing
When: Periodic
Why: Monitor for immunogenicity
Serum latent myostatin
When: Periodic
Why: Confirm pharmacodynamic target engagement
๐ก Key Considerations
- โNot yet FDA-approved: BLA filed but received a Complete Response Letter related to manufacturing
- โMonoclonal antibody requiring IV administration: not available from peptide suppliers
- โMust be used as adjunct to SMN-targeted therapy; not tested as monotherapy for SMA
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| Purpose | Dose | Frequency | Duration | Notes |
|---|---|---|---|---|
| SMA Motor Function (SAPPHIRE Phase 3) | Apitegromab 10 mg/kg or 20 mg/kg IV every 4 weeks for 12 months in nonambulatory patients with Types 2 and 3 SMA aged 2-21 receiving nusinersen or risdiplam. Both doses contributed to a pooled 1.8-point HFMSE improvement over placebo (p=0.019). | IV infusion every 4 weeks (Q4W) | 12 months in the pivotal study | Randomized 1:1:1 to 10 mg/kg, 20 mg/kg, or placebo. Primary analysis pooled both dose groups. Individual dose-response differentiation not clearly reported. Background SMN-targeted therapy required in all participants. |
| SMA Motor Function (TOPAZ Phase 2) | Apitegromab 2, 10, or 20 mg/kg IV every 4 weeks in patients with Types 2 and 3 SMA aged 2-21. The 20 mg/kg dose in nonambulatory patients receiving nusinersen showed the strongest HFMSE improvements at 36-48 months. | IV infusion every 4 weeks (Q4W) | 12 months core study, extended to 48 months | Open-label active treatment design (no placebo). Long-term extension data showed sustained motor function gains. 48-month HFMSE change of +5.3 points at 20 mg/kg with nusinersen. |
| Obesity/Lean Mass Preservation (EMBRAZE Phase 2) | Apitegromab 10 mg/kg IV every 4 weeks in combination with tirzepatide in adults with BMI >=27 with comorbidities or BMI >=30. Preserved 54.9% of lean mass (p=0.001) vs tirzepatide alone at 24 weeks. | IV infusion every 4 weeks (Q4W) | 24 weeks | Proof-of-concept trial (n=100). Randomized 1:1 to apitegromab or placebo, all receiving tirzepatide. No serious adverse events or discontinuations related to apitegromab. Scholar Rock plans to develop SRK-439 (next-generation inhibitor) for the obesity indication. |
| Phase 1 Dose-Finding (Healthy Adults) | Single ascending doses of 1, 3, 10, 20, 30 mg/kg IV and multiple ascending doses of 10, 20, 30 mg/kg IV in healthy adults. Linear, dose-proportional pharmacokinetics with half-life of 24-31 days. | Single dose or multiple doses IV | Variable (Phase 1) | Safe and well-tolerated at all doses up to 30 mg/kg. No anti-drug antibodies detected. Dose-dependent target engagement confirmed by serum latent myostatin increases. |
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๐Reconstitution Instructions
Apitegromab is supplied as a sterile solution for IV infusion in clinical trial settings. It does not require reconstitution by end users. All preparation and administration occurs within clinical trial sites under medical supervision.
๐งStorage Requirements
As a monoclonal antibody, apitegromab requires refrigerated storage (2-8 degrees C) and protection from light. It must not be frozen. Storage and handling are managed by clinical trial sites per sponsor protocols.
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Before You Begin
Review safety warnings and contraindications before starting any protocol.
Investigational Drug Status#
Apitegromab has submitted a BLA to the FDA for SMA but has not yet received marketing approval. It is currently accessible only through clinical trials. All dosing information below is from published clinical trial data.
Administration Route#
Apitegromab is administered as an intravenous (IV) infusion, similar to bimagrumab but unlike trevogrumab (which uses subcutaneous injection). IV administration requires:
- Clinical site with infusion capability
- Healthcare professional supervision
- Infusion monitoring period
- Clinic visits every 4 weeks
For SMA patients who are already receiving IV nusinersen (Spinraza) at treatment centers, the addition of IV apitegromab infusions may be logistically manageable. However, for the obesity indication, IV administration represents a practical limitation compared to SC alternatives.
Clinical Trial Dosing#
SMA Dosing (SAPPHIRE Phase 3)#
| Parameter | Value |
|---|---|
| Doses tested | 10 mg/kg and 20 mg/kg |
| Route | Intravenous infusion |
| Frequency | Every 4 weeks (Q4W) |
| Duration | 12 months |
| Population | Nonambulatory SMA Types 2/3, ages 2-21 |
| Background therapy | Nusinersen or risdiplam required |
| Primary endpoint | HFMSE change from baseline (MET) |
SMA Long-Term Dosing (TOPAZ Extension)#
| Parameter | Value |
|---|---|
| Optimal dose | 20 mg/kg (strongest long-term response) |
| Duration | Up to 48 months |
| HFMSE at 48 months | +5.3 points (20 mg/kg + nusinersen) |
| Safety | Consistent with 12-month profile |
Obesity Dosing (EMBRAZE Phase 2)#
| Parameter | Value |
|---|---|
| Apitegromab dose | 10 mg/kg |
| Route | Intravenous infusion |
| Frequency | Every 4 weeks (Q4W) |
| Duration | 24 weeks |
| Background therapy | Tirzepatide |
| Key result | 54.9% lean mass preservation (p=0.001) |
Phase 1 Dosing (Healthy Adults)#
| Parameter | Single Dose | Multiple Dose |
|---|---|---|
| Doses tested | 1, 3, 10, 20, 30 mg/kg | 10, 20, 30 mg/kg |
| Half-life | 24-31 days | Consistent with single dose |
| PK profile | Linear, dose-proportional | Linear, dose-proportional |
Dose Comparison Across Indications#
| Study | Dose | Frequency | Duration | Key Result |
|---|---|---|---|---|
| SAPPHIRE (SMA) | 10-20 mg/kg | Q4W IV | 12 months | +1.8 HFMSE (p=0.019) |
| TOPAZ (SMA) | 2-20 mg/kg | Q4W IV | 48 months | +5.3 HFMSE (20 mg/kg) |
| EMBRAZE (Obesity) | 10 mg/kg | Q4W IV | 24 weeks | 54.9% lean preserved |
| Phase 1 | 1-30 mg/kg | Single/multiple IV | Variable | PK/PD established |
Not Available for Self-Administration#
Key points about apitegromab availability:
- Not yet approved: BLA filed but CRL received; approval pending
- IV administration only: Requires clinical infusion site
- Not a peptide: Cannot be synthesized by peptide suppliers
- Monoclonal antibody: Requires mammalian cell production and GMP manufacturing
- SRK-439: Scholar Rock is developing a next-generation myostatin inhibitor potentially with SC formulation for obesity
Related Reading#
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Medical Disclaimer
This website is for educational and informational purposes only. The information provided is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before using any peptide or supplement.