Aldoxorubicin Explained

Iupac Name:	N-1-[(2''S'',4''S'')-4-[(2''R'',4''S'',5''S'',6''S'')-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-hydroxyethylideneamino]-6-(2,5-dioxopyrrol-1-yl)hexanamide
Cas Number:	1361644-26-9
Unii:	C28MV4IM0B
Pubchem:	71300693
Chemspiderid:	7986464
Kegg:	D10383
C:	37
H:	42
N:	4
O:	13
Stdinchikey:	OBMJQRLIQQTJLR-FRTGXRTISA-N
Stdinchi:	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
Smiles:	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

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).

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

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. In November 2016, CytRx announced that preliminary results had been positive.^[1]

Further reading

• Kratz F, Azab S, Zeisig R, Fichtner I, Warnecke A . Evaluation of combination therapy schedules of doxorubicin and an acid-sensitive albumin-binding prodrug of doxorubicin in the MIA PaCa-2 pancreatic xenograft model . International Journal of Pharmaceutics . 441 . 1–2 . 499–506 . January 2013 . 23149257 . 10.1016/j.ijpharm.2012.11.003 .
• Walker L, Perkins E, Kratz F, Raucher D . Cell penetrating peptides fused to a thermally targeted biopolymer drug carrier improve the delivery and antitumor efficacy of an acid-sensitive doxorubicin derivative . International Journal of Pharmaceutics . 436 . 1–2 . 825–32 . October 2012 . 22850291 . 3465682 . 10.1016/j.ijpharm.2012.07.043 .
• Kratz F, Warnecke A . Finding the optimal balance: challenges of improving conventional cancer chemotherapy using suitable combinations with nano-sized drug delivery systems . Journal of Controlled Release . 164 . 2 . 221–35 . December 2012 . 22705248 . 10.1016/j.jconrel.2012.05.045 .
• Sanchez E, Li M, Wang C, Nichols CM, Li J, Chen H, Berenson JR . Anti-myeloma effects of the novel anthracycline derivative INNO-206 . Clinical Cancer Research . 18 . 14 . 3856–67 . July 2012 . 22619306 . 10.1158/1078-0432.CCR-11-3130 . 7467600 .

Notes and References

1. Web site: CytRx (CYTR) Announces Statistically Significant Data from Aldoxorubicin Phase 3 in r/r STS . 29 November 2016 .