The Role of Complement Activation in Hypersensitivity to Pegylated Liposomal Doxorubicin (Doxil®)

Abstract

Liposomal formulations of some drugs, most importantly pegylated lipo-soma1 doxorubicin (Doxil@), have been reported to cause immediate hypersensitivity reactions that cannot be explained with the conventional paradigm of IgE-mediated (type I) allergy. Here we present a rationale and experimental evidence for the concept that these reactions represent a novel type of druginduced hypersensitivity that can be called complement (C) activation-related pseudoallergy (CARPA). The theoretical foundation includes the facts that 1) some liposomes have been known to activate C, 2) most of the clinical symptoms of liposome-induced reactions coincide with those caused by C activation by other activators, and 3) the C mechanism explains those manifestations which are atypical for type 1 reactions. The experimental the observations that 1 ) Doxil caused massive C activati (4/10) of normal human sera, 2) high dose IgG attenuated Doxil-induced C activation in serum and prevented further C activation by amplification, and 3) intravenous injection of therapeutically relevant doses of Doxil in pigs caused Journal of Liposome Research Downloaded from informahealthcare.com by The University of Manchester on 11/19/14 For personal use only. -168 SZERENI ET AL.significant pulmonary hypertension with consequent systemic hypotension and decline of cardiac output, which changes mimicked the cardiovascular manifestations of the human reaction and were shown to be triggered by C activation. As for the question how Doxil, a long-circulating "stealth" liposome forniulation, avoids phagocytic uptake by macrophages despite its potential opsonization by C3b, we demonstrated efficient inactivation of Doxil-bound and free C3b to iC3b in human serum. Thus, it i s unlikely that PEG would interfere with CDI 1 b/CD18-mediated phagocytosis by inhibiting the formation of its main ligand, iC3b.

Liposome-induced complement activation and related cardiopulmonary distress in pigs: factors promoting reactogenicity of Doxil and AmBisome

“…As positive controls for liposome-induced C activation and cardiopulmonary reactions we used multilamellar DMPCChol-DMPG liposomes (MLVs) and zymosan, which were shown earlier to be potent C activators and CARPA inducers in pigs. [13][14][15][16] Analysis of the effects of the above vesicle parameters in a Doxil-sensitive NHS showed major and minor impacts. The two liposome variables that led to major increases in C activation were the presence of doxorubicin and expressed net negative surface charge on vesicles, whereas all other listed permutations of surface properties caused minor impact on SC5b-9 formation.…”

“…10 The present study focused primarily on C activation and in vivo reactogenicity of Doxil, the first liposomal nanomedicine, which has been for many years successfully used in cancer chemotherapy. 6,7,[28][29][30][31][32][33]38 Initially it was thought that steric stabilization with PEG should protect against C binding to liposomes 39 ; however, more recent studies proved that Doxil is a strong C activator, 14,37 partly as a consequence of the net anionic charge of the phosphate moiety on 2K-PEG-PE. 17 To explore further structural features of Doxil that might contribute to C activation, here we performed head-to-head comparison of C activation and in vivo reactogenicity of commercial Doxil and equivalent drug-free vesicles, differing from Doxil and from each other in one feature at a time.…”

“…The clinical relevance of the subject lies in the increased risk for non-IgEmediated infusion reactions in patients treated for the first time with many liposomal drugs, including Doxil, AmBisome, Abelcet, Amphocyl, and Daunoxome. [10][11][12]14,16,[28][29][30][31][32][33][34][35][36] Although slow initial infusion and premedication with corticosteroids and antihistamines are effective in reducing the frequency of CARPA, 37 reactions still occur in up to 10% of patients treated with Doxil despite slow infusion and/or premedication. 10 The present study focused primarily on C activation and in vivo reactogenicity of Doxil, the first liposomal nanomedicine, which has been for many years successfully used in cancer chemotherapy.…”

“…14 Also, in preliminary studies we found that different Doxil or Calyx batches display different capabilities to activate C in NHS. Thus, for the present dissection of liposomal structural factors contributing to C activation, we used a preselected highly reactive Doxil batch as the source of liposomal doxorubicin (i.e., Doxil) and a highly reactive NHS as serum source.…”

PEGylation of microspheres generates a heterogeneous population of particles with differential surface characteristics and biological performance

“…For example, Doxil 0 , a PEGylated liposomal formulation containing doxorubicin, has a biphasic circulation half-life of 84 min and 46 h in humans, respectively [17]. In addition to this, Doxil 0 is a potent activator of the human complement system with activation taking place within minutes [18]. Doxil 0 contains 5^7 mol% mPEG^phospholipid with surface-projected mPEG chains in a mushroom^brush con¢gura-tion, which explain the prolonged circulation times of the vesicles.…”