Hematopoietic Growth Factors

Erythropoiesis-Stimulating Agents - Red Cell Rally

ESAs mimic endogenous erythropoietin (EPO).

• Agents: Epoetin alfa, Darbepoetin alfa (longer-acting), Methoxy PEG-epoetin beta.
• MOA: Activate JAK-STAT pathway on erythroid precursors; increase RBC production.
• Pharmacokinetics: IV/SC.

  Feature	Epoetin Alfa	Darbepoetin Alfa
  Half-life (IV)	4-13 hrs	~21 hrs (longer)
  Glycosylation	Standard	Increased sialic acid

• Clinical Uses:
  • Anemia of CKD (target Hb 10-12 g/dL)
  • Chemo-induced anemia (non-myeloid)
  • Zidovudine-induced anemia (HIV)
  • Anemia in MDS
  • Reduce allogeneic transfusions (surgery).
• Adverse Effects:
  • Hypertension (most common)
  • Thrombotic events (MI, stroke, VTE): Risk if Hb > 11-12 g/dL or rises > 1 g/dL/2 wks.
  • PRCA (antibody-mediated)
  • Seizures
  • Potential tumor progression
  • 📌 Mnemonic: EPO causes HHH - Hypertension, Hypercoagulability, Hyperviscosity.
• Cautions/CI:
  • Uncontrolled hypertension, known hypersensitivity, history of PRCA.
  • Caution: cancer patients not receiving chemotherapy.
• Monitoring: Monitor: Hb (target 10-12 g/dL, avoid rise > 1 g/dL/2 wks), iron, BP.

⭐ Darbepoetin alfa's significantly longer half-life compared to epoetin alfa is due to its increased sialic acid content from additional glycosylation sites.

Myeloid Growth Factors - Neutrophil Ninjas

Stimulate myeloid progenitor proliferation & differentiation.

• G-CSF (Granulocyte Colony-Stimulating Factor)

  • Agents: Filgrastim, Pegfilgrastim (long-acting), Lenograstim.
  • MOA: ↑ Neutrophil lineage. 📌 G-CSF for Granulocytes.
  • Clinical Uses:
    • Chemotherapy-induced neutropenia (prophylaxis & treatment, esp. ANC < 500/µL).
    • Bone Marrow Transplant (BMT): PBSC mobilization, accelerates post-transplant neutrophil recovery.
    • Aplastic anemia, congenital neutropenias, Myelodysplastic Syndromes (MDS).
  • Adverse Effects:
    • Bone pain (common), flu-like symptoms, splenic rupture (rare), ARDS.

  ⭐ Pegfilgrastim, a pegylated G-CSF, has a prolonged half-life due to reduced renal clearance, allowing for once-per-chemotherapy-cycle dosing.

• GM-CSF (Granulocyte-Macrophage CSF)

  • Agents: Sargramostim, Molgramostim.
  • MOA: Broader: ↑ neutrophils, eosinophils, monocytes, macrophages. 📌 GM-CSF for Granulocytes & Macrophages.
  • Clinical Uses:
    • Chemotherapy-induced neutropenia.
    • BMT (post-transplant recovery, engraftment failure).
    • Aplastic anemia.
  • Adverse Effects:
    • Fever, myalgia, arthralgia, rash, capillary leak syndrome, effusions, first-dose reaction (hypotension, dyspnea).

Thrombopoietic Growth Factors - Platelet Promoters

• TPO Receptor Agonists (TPO-RAs):
  • Agents & PK:
    • Romiplostim (SC).
    • Eltrombopag (Oral; chelation with $Ca^{2+}$ - take empty stomach/low-$Ca^{2+}$ meal).
    • Avatrombopag (Oral), Lusutrombopag (Oral).
  • MOA: Mimic TPO → stimulate megakaryopoiesis → ↑ platelet production.
  • Uses:
    • Chronic ITP (target platelets > 50,000/µL).
    • Thrombocytopenia in CLD (pre-procedure).
    • Severe aplastic anemia (Eltrombopag).
  • AEs: Headache, arthralgia, myalgia, marrow reticulin fibrosis (monitor), thromboembolism. Rebound thrombocytopenia (on discontinuation).
    • Eltrombopag: Hepatotoxicity (monitor LFTs).

⭐ Eltrombopag is an oral, non-peptide TPO receptor agonist that must be taken on an empty stomach or with a low-calcium meal to avoid chelation with polyvalent cations.

• Interleukin-11 (IL-11):
  • Agent & PK: Oprelvekin (SC) - less used.
  • MOA: Stimulates various hematopoietic cells, including megakaryocyte progenitors.
  • Uses: Prevention of severe thrombocytopenia post-myelosuppressive chemo (non-myeloid malignancies).
  • AEs: Fluid retention (edema, dyspnea), atrial arrhythmias (tachycardia, fibrillation), fatigue, headache. 📌 Oprelvekin (IL-11) makes you 'swell-even'.

High‑Yield Points - ⚡ Biggest Takeaways

• Erythropoietin (EPO) & Darbepoetin alfa stimulate RBCs; treat anemia of CKD.
• G-CSF (Filgrastim, Pegfilgrastim) boosts neutrophils; for chemotherapy-induced neutropenia.
• GM-CSF (Sargramostim) stimulates myeloid lineages; used in aplastic anemia, BMT.
• TPO agonists (Romiplostim, Eltrombopag) ↑ platelets; treat ITP.
• EPO adverse effects: hypertension, thrombosis, pure red cell aplasia (PRCA).
• Oprelvekin (IL-11) ↑ platelets; side effects (fluid retention) limit use.
• Monitor hemoglobin with EPO; target <12 g/dL to avoid thrombosis.