title: Anti-CD30 diabody-drug conjugates with potent antitumor activity.
abstract: 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.
authors: Seattle Genetics, Inc., 21823 30th Drive Southeast, Bothell, WA 98021, USA. kkim@seagen.com
authors: Kristine M
authors: KM
authors: Kim
authors: Charlotte F
authors: CF
authors: McDonagh
authors: Lori
authors: L
authors: Westendorf
authors: Lindsay L
authors: LL
authors: Brown
authors: Django
authors: D
authors: Sussman
authors: Tiffany
authors: T
authors: Feist
authors: Robert
authors: R
authors: Lyon
authors: Stephen C
authors: SC
authors: Alley
authors: Nicole M
authors: NM
authors: Okeley
authors: Xinqun
authors: X
authors: Zhang
authors: Melissa C
authors: MC
authors: Thompson
authors: Ivan
authors: I
authors: Stone
authors: Hans-Peter
authors: HP
authors: Gerber
authors: Paul J
authors: PJ
authors: Carter
mesh_terms: 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*
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D007074:Immunoglobulin G; D017730:Ki-1 Antigen