Aldoxorubicin

Aldoxorubicin (INNO-206) is a tumor-targeted doxorubicin conjugate in development by CytRx. Specifically, it is the (6-maleimidocaproyl) hydrazone of doxorubicin. Essentially, this chemical name describes doxorubicin attached to an acid-sensitive linker (N-ε-maleimidocaproic acid hydrazide, or EMCH).

Aldoxorubicin
Identifiers
  • N-[[1-[(2S,4S)-4-[(2R,4S,5S,6S)-4-Amino-5-hydroxy-6-methyloxan-2-yl]oxy-2,5,12-trihydroxy-7-methoxy-6,11-dioxo-3,4-dihydro-1H-tetracen-2-yl]-2-hydroxyethylidene]amino]-6-(2,5-dioxopyrrol-1-yl)hexanamide
CAS Number
PubChem CID
ChemSpider
UNII
KEGG
ECHA InfoCard100.244.879
Chemical and physical data
FormulaC37H42N4O13
Molar mass750.758 g·mol−1
3D model (JSmol)
  • C[C@H]1[C@H]([C@H](C[C@@H](O1)O[C@H]2C[C@@](CC3=C(C4=C(C(=C23)O)C(=O)C5=C(C4=O)C=CC=C5OC)O)(C(=NNC(=O)CCCCCN6C(=O)C=CC6=O)CO)O)N)O
  • InChI=1S/C37H42N4O13/c1-17-32(46)20(38)13-27(53-17)54-22-15-37(51,23(16-42)39-40-24(43)9-4-3-5-12-41-25(44)10-11-26(41)45)14-19-29(22)36(50)31-30(34(19)48)33(47)18-7-6-8-21(52-2)28(18)35(31)49/h6-8,10-11,17,20,22,27,32,42,46,48,50-51H,3-5,9,12-16,38H2,1-2H3,(H,40,43)/t17-,20-,22-,27-,32+,37-/m0/s1
  • Key:OBMJQRLIQQTJLR-FRTGXRTISA-N

The proposed mechanism of action is as follows:

  1. After administration, aldoxorubicin rapidly binds endogenous circulating albumin through the EMCH linker.
  2. Circulating albumin preferentially accumulates in tumors, bypassing uptake by other non-specific sites including heart, bone marrow and gastrointestinal tract.
  3. Once albumin-bound aldoxorubicin reaches the tumor, the acidic environment of the tumor causes cleavage of the acid sensitive linker.
  4. Free doxorubicin is released at the site of the tumor.

Clinical trials

Five phase I trials for safety characterization have been completed. Several phase II and III trials are underway.

Phase II

As of January 2017, there are 6 phase II clinical trials in progress:

  1. Second-line therapy for patients with glioblastoma[1]
  2. Treatment of HIV-positive patients with Kaposi's sarcoma[2]
  3. Combination therapy of ifosfamide and aldoxorubicin for treatment of metastatic or locally advanced sarcoma[3]
  4. Comparison of aldoxorubicin to the gold-standard treatment, topotecan, for metastatic small cell lung cancer[4]
  5. Treatment of advanced or metastatic pancreatic ductal adenocarcinoma[5]
  6. Comparison of aldoxorubicin and doxorubicin for patients with metastatic or locally advanced carcinoma[6]

Phase III

A phase III trial for patients with relapsed soft tissue sarcoma comparing aldoxorubicin with several other chemotherapeutics is expected to complete in 2018.[7] In November 2016, CytRx announced that preliminary results had been positive.[8]

References
  1. Clinical trial number NCT02014844 for "Phase 2 Study to Investigate the Efficacy and Safety of Aldoxorubicin in Subjects With Glioblastoma" at ClinicalTrials.gov
  2. Clinical trial number NCT02029430 for "A Study to Investigate ALDOXORUBICIN in HIV-infected Subjects With Kaposi's Sarcoma" at ClinicalTrials.gov
  3. Clinical trial number NCT02235701 for "Study to Investigate the Safety and Activity of Aldoxorubicin Plus Ifosfamide/Mesna in Subjects With Metastatic Soft Tissue Sarcoma" at ClinicalTrials.gov
  4. Clinical trial number NCT02200757 for "Efficacy and Safety of Aldoxorubicin Compared to Topotecan in Subjects With Metastatic Small Cell Lung Cancer" at ClinicalTrials.gov
  5. Clinical trial number NCT01580397 for "Pilot Phase 2 Study to Investigate the Preliminary Efficacy and Safety of INNO-206 in Advanced Pancreatic Cancer" at ClinicalTrials.gov
  6. Clinical trial number NCT01514188 for "Preliminary Efficacy and Safety of INNO-206 Compared to Doxorubicin in Advanced Soft Tissue Sarcoma" at ClinicalTrials.gov
  7. Clinical trial number NCT02049905 for "Phase 3 Study to Treat Patients With Soft Tissue Sarcomas" at ClinicalTrials.gov
  8. "CytRx (CYTR) Announces Statistically Significant Data from Aldoxorubicin Phase 3 in r/r STS". 29 November 2016.

Further reading
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