Anti-CD30 diabody-drug conjugates with potent antitumor activity.
Anti-CD30 diabodies were engineered with two cysteine mutations for site-specific drug conjugation in each chain of these homodimeric antibody fragments. Diabodies were conjugated with approximately 4 equivalents of the anti-tubulin drugs, monomethyl auristatin E or F, via a protease-cleavable dipeptide linker, to create the conjugates, diabody-vcE4 and diabody-vcF4, respectively. Diabody conjugation had only minor (<3-fold) effects on antigen binding. Diabody-vcF4 was potently cytotoxic against the antigen-positive cell lines, Karpas-299 (34 pmol/L IC(50)) and L540cy (22 pmol/L IC(50)), and was 8- and 21-fold more active than diabody-vcE4 against these cell lines, respectively. Clearance of diabody-vcF4 (99-134 mL/d/kg) was 5-fold slower than for the nonconjugated diabody in naive severe combined immunodeficient mice. Diabody-vcF4 had potent and dose-dependent antitumor activity against established Karpas-299 xenografts and gave durable complete responses at well-tolerated doses. Biodistribution experiments with diabody-[(3)H]-vcF4 (0.72-7.2 mg/kg) in tumor-bearing mice showed a dose-dependent increase in total auristatin accumulation in tumors (< or =520 nmol/L) and decrease in relative auristatin accumulation (< or =8.1 %ID/g), with peak localization at 4 to 24 h after dosing. Diabody-vcF4 had approximately 4-fold lower cytotoxic activity than the corresponding IgG1-vcF4 conjugate in vitro. A similar potency difference was observed in vivo despite 25- to 34-fold faster clearance of diabody-vcF4 than IgG1-vcF4. This may reflect that dose-escalated diabody-vcF4 can surpass IgG1-vcF4 in auristatin delivery to tumors, albeit with higher auristatin exposure to some organs including kidney and liver. Diabody-drug conjugates can have potent antitumor activity at well-tolerated doses and warrant further optimization for cancer therapy.
Kim
Kristine M
KM
Seattle Genetics, Inc., 21823 30th Drive Southeast, Bothell, WA 98021, USA. kkim@seagen.com
McDonagh
Charlotte F
CF
Westendorf
Lori
L
Brown
Lindsay L
LL
Sussman
Django
D
Feist
Tiffany
T
Lyon
Robert
R
Alley
Stephen C
SC
Okeley
Nicole M
NM
Zhang
Xinqun
X
Thompson
Melissa C
MC
Stone
Ivan
I
Gerber
Hans-Peter
HP
Carter
Paul J
PJ
D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000276:immunology / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D005260:Female; D007074:Immunoglobulin G / Q000276:immunology; D017730:Ki-1 Antigen / Q000037:antagonists & inhibitors* / Q000276:immunology; D051379:Mice; D016513:Mice, SCID; D009369:Neoplasms / Q000188:drug therapy*
D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D007074:Immunoglobulin G; D017730:Ki-1 Antigen