MC-SN38 is an active molecular conjugate consisting of the potent microtubule-destroying agent SN38 and a non-cleavable (non-degradable) MC linker. It is used to synthesize antibody active molecular conjugates (ADC). SN-38 is the bioactive metabolite of the topoisomerase I inhibitor irinotecan, which inhibits DNA synthesis and causes DNA single-strand breaks.

Physicochemical Properties

Molecular Formula	C32H31N3O8
Molecular Weight	585.60
Exact Mass	585.211
Elemental Analysis	C, 65.63; H, 5.34; N, 7.18; O, 21.86
CAS #	1473403-87-0
PubChem CID	146673122
Appearance	White to yellow solid powder
LogP	2.3
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	9
Rotatable Bond Count	10
Heavy Atom Count	43
Complexity	1300
Defined Atom Stereocenter Count	1
SMILES	O=C1C=CC(=O)N1CCCCCC(O[C@@]1(C(OCC2C(N3CC4=C(CC)C5=CC(=CC=C5N=C4C3=CC=21)O)=O)=O)CC)=O
InChi Key	ACRMADURFCYBAU-YTTGMZPUSA-N
InChi Code	InChI=1S/C32H31N3O8/c1-3-19-20-14-18(36)9-10-24(20)33-29-21(19)16-35-25(29)15-23-22(30(35)40)17-42-31(41)32(23,4-2)43-28(39)8-6-5-7-13-34-26(37)11-12-27(34)38/h9-12,14-15,36H,3-8,13,16-17H2,1-2H3/t32-/m0/s1
Chemical Name	[(19S)-10,19-diethyl-7-hydroxy-14,18-dioxo-17-oxa-3,13-diazapentacyclo[11.8.0.02,11.04,9.015,20]henicosa-1(21),2,4(9),5,7,10,15(20)-heptaen-19-yl] 6-(2,5-dioxopyrrol-1-yl)hexanoate
Synonyms	MC-SN38; 1473403-87-0; AKOS040756843; [(19S)-10,19-diethyl-7-hydroxy-14,18-dioxo-17-oxa-3,13-diazapentacyclo[11.8.0.02,11.04,9.015,20]henicosa-1(21),2,4(9),5,7,10,15(20)-heptaen-19-yl] 6-(2,5-dioxopyrrol-1-yl)hexanoate;
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

Targets	Camptothecins/DNA Topoisomerase I; Drug-linker conjugate for ADC
ln Vitro	It is known that 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11), a semisynthesized derivative of camptothecin (CPT), has a potent antitumor activity in vivo, but 7-ethyl-10-hydroxycamptothecin (SN-38), a metabolite of CPT-11, shows much stronger cytotoxicity in vitro than CPT-11. In this study, we demonstrated that the relaxation of SV40 DNA plasmids by type I DNA topoisomerase prepared from P388 murine leukemia cells was inhibited by 50% by SN-38 at approximately 1 microM, although CPT-11 at 1 mM slightly inhibited the relaxation. SN-38 and CPT showed strong, time-dependent inhibitory activity against DNA synthesis of P388 cells. However, CPT-11 weakly inhibited DNA synthesis independently of time with coincident inhibition of the total thymidine uptake by the cells. By alkaline and neutral elution assays, it was demonstrated that SN-38 caused much more frequent DNA single-strand breaks in P388 cells than did CPT-11. The same content of SN-38 and a similar frequency of single-strand breaks were detected in the cells treated with SN-38 at 0.1 microM or with CPT-11 at 100 microM. Therefore, single-strand breaks by CPT-11 seem to be due to SN-38 produced from CPT-11 in cells. These results indicate that CPT-11 itself possesses a marginal antiproliferative effect but that SN-38 plays an essential role in the mechanism of action of CPT-11[2].
References	[1]. Characterization of DNA topoisomerase I in three SN-38 resistant human colon cancer cell lines reveals a newpair of resistance-associated mutations. J Exp Clin Cancer Res. 2016 Mar 31;35:56. [2]. Intracellular roles of SN-38, a metabolite of the camptothecin derivative CPT-11, in the antitumor effect of CPT-11. Cancer Res. 1991;51(16):4187-4191.
Additional Infomation	DNA topoisomerase I (Top1) is a DNA unwinding protein and the specific target of the camptothecin class of chemotherapeutic drugs. One of these, irinotecan, acting through its active metabolite SN-38, is used in the treatment of metastatic colorectal cancer. However, resistance to irinotecan represents a major clinical problem. Since molecular alterations in Top1 may result in resistance to irinotecan, we characterized Top1 in three human colon cancer cell lines with acquired resistance to SN-38. Methods: Three SN-38 resistant (20-67 fold increased resistance) cell lines were generated and compared to wild-type parental cells with regards to: TOP1 gene copy number and gene sequence, Top1 expression (mRNA and protein), Top1 enzymatic activity in the absence and presence of drug, and Top1-DNA cleavage complexes in drug treated cells. TOP1 mutations were validated by PCR using mutant specific primers. Furthermore, cross-resistance to two indenoisoquinoline Top1-targeting drugs (NSC 725776 and NSC 743400) and two Top2-targeting drugs (epirubicin and etoposide) was investigated. Results: Two of three SN-38 resistant cell lines carried TOP1 gene copy number aberrations: A TOP1 gene copy gain and a loss of chromosome 20, respectively. One resistant cell line harbored a pair of yet unreported TOP1 mutations (R364K and G717R) in close proximity to the drug binding site. Mutant TOP1 was expressed at a markedly higher level than wild-type TOP1. None or very small reductions were observed in Top1 expression or Top1 activity in the absence of drug. In all three SN-38 resistant cell lines Top1 activity was maintained in the presence of high concentrations of SN-38. None or only partial cross-resistance were observed for etoposide and epirubicin, respectively. SN-38 resistant cells with wild-type TOP1 remained sensitive to NSC 743400, while cells with mutant TOP1 was fully cross-resistant to both indenoisoquinolines. Top1-DNA cleavage complex formation following drug treatment supported the other findings. Conclusions: This study adds to the growing knowledge about resistance mechanisms for Top1-targeting chemotherapeutic drugs. Importantly, two yet unreported TOP1 mutations were identified, and it was underlined that cross-resistance to the new indenoisoquinoline drugs depends on the specific underlying molecular mechanism of resistance to SN-38.[1]

Solubility Data

Solubility (In Vitro)

DMSO : 140 mg/mL (239.07 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 5.75 mg/mL (9.82 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 57.5 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: 5.75 mg/mL (9.82 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 57.5 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	1.7077 mL	8.5383 mL	17.0765 mL
	5 mM	0.3415 mL	1.7077 mL	3.4153 mL
	10 mM	0.1708 mL	0.8538 mL	1.7077 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.