Development of Targeted Alpha Particle Therapy for Solid Tumors

Abstract: Targeted alpha-particle therapy (TAT) aims to selectively deliver radionuclides emitting α-particles (cytotoxic payload) to tumors by chelation to monoclonal antibodies, peptides or small molecules that recognize tumor-associated antigens or cell-surface receptors. Because of the high linear energy transfer (LET) and short range of alpha (α) particles in tissue, cancer cells can be significantly damaged while causing minimal toxicity to surrounding healthy cells. Recent clinical studies have demonstrated the remarkable efficacy of TAT in the treatment of metastatic, castration-resistant prostate cancer. In this comprehensive review, we discuss the current consensus regarding the properties of the α-particle-emitting radionuclides that are potentially relevant for use in the clinic; the TAT-mediated mechanisms responsible for cell death; the different classes of targeting moieties and radiometal chelators available for TAT development; current approaches to calculating radiation dosimetry for TATs; and lead optimization via medicinal chemistry to improve the TAT radiopharmaceutical properties. We have also summarized the use of TATs in pre-clinical and clinical studies to dat

Inflammatory Genital Infections Mitigate a Severe Genetic Bottleneck in Heterosexual Transmission of Subtype A and C HIV-1

The HIV-1 epidemic in sub-Saharan Africa is driven largely by heterosexual transmission of non-subtype B viruses, of which subtypes C and A are predominant. Previous studies of subtype B and subtype C transmission pairs have suggested that a single variant from the chronically infected partner can establish infection in their newly infected partner. However, in subtype A infected individuals from a sex worker cohort and subtype B individuals from STD clinics, infection was frequently established by multiple variants. This study examined over 1750 single-genome amplified viral sequences derived from epidemiologically linked subtype C and subtype A transmission pairs very early after infection. In 90% (18/20) of the pairs, HIV-1 infection is initiated by a single viral variant that is derived from the quasispecies of the transmitting partner. In addition, the virus initiating infection in individuals who were infected by someone other than their spouse was characterized to determine if genital infections mitigated the severe genetic bottleneck observed in a majority of epidemiologically linked heterosexual HIV-1 transmission events. In nearly 50% (3/7) of individuals infected by someone other than their spouse, multiple genetic variants from a single individual established infection. A statistically significant association was observed between infection by multiple genetic variants and an inflammatory genital infection in the newly infected individual. Thus, in the vast majority of HIV-1 transmission events in cohabiting heterosexual couples, a single genetic variant establishes infection. Nevertheless, this severe genetic bottleneck can be mitigated by the presence of inflammatory genital infections in the at risk partner, suggesting that this restriction on genetic diversity is imposed in large part by the mucosal barrier

Promotion of couples’ voluntary HIV counseling and testing: a comparison of influence networks in Rwanda and Zambia

Abstract Background Many African adults do not know that partners in steady or cohabiting relationships can have different HIV test results. Despite WHO recommendations for couples’ voluntary counseling and testing (CVCT), fewer than 10 % of couples have been jointly tested and counseled. We examine the roles and interactions of influential network leaders (INLs) and influential network agents (INAs) in promoting CVCT in Kigali, Rwanda and Lusaka, Zambia. Methods INLs were identified in the faith-based, non-governmental, private, and health sectors. Each INL recruited and mentored several INAs who promoted CVCT. INLs and INAs were interviewed about demographic characteristics, promotional efforts, and working relationships. We also surveyed CVCT clients about sources of CVCT information. Results In Zambia, 53 INAs and 31 INLs were surveyed. In Rwanda, 33 INAs and 27 INLs were surveyed. Most (75 %–90 %) INAs believed that INL support was necessary for their promotional work. Zambian INLs reported being more engaged with their INAs than Rwandan INLs, with 58 % of Zambian INLs reporting that they gave a lot of support to their INAs versus 39 % in Rwanda. INAs in both Rwanda and Zambia reported promoting CVCT via group forums (77 %–97 %) and speaking to a community leader about CVCT (79 %–88 %) in the past month. More Rwandan INAs and INLs reported previous joint or individual HIV testing compared with their Zambian counterparts, of which more than half had not been tested. In Zambia and Rwanda, 1271 and 3895 CVCT clients were surveyed, respectively. Hearing about CVCT from INAs during one-on-one promotions was the most frequent source of information reported by clients in Zambia (71 %). In contrast, Rwandan couples who tested were more likely to have heard about CVCT from a previously tested couple (59 %). Conclusions CVCT has long been endorsed for HIV prevention but few couples have been reached. Influential social networks can successfully promote evidence-based HIV prevention in Africa. Support from more senior INLs and group presentations leveraged INAs’ one-on-one promotions. The INL/INA model was effective in promoting couples to seek joint HIV testing and counseling and may have broader application to other sub-Saharan African countries to sustainably increase CVCT uptake

Client-initiated violence against Zambian female sex workers : prevalence and associations with behavior, environment, and sexual history

Violence against women is a known risk factor for HIV and affects female sex workers (FSW) in sub-Saharan Africa. Little is known about the magnitude and determinants of violence against FSW in Zambia, where HIV and gender-based violence prevalence are high. We conducted a cross-sectional study, using multivariable logistic regression, to determine the prevalence and correlates of client-initiated physical violence among 419 FSW in Lusaka and Ndola. The prevalence of client-initiated physical violence was 39%. The odds of violence were higher for FSW who: lived in Lusaka, recruited clients from the street, serviced clients in the clients' homes, had a physically forced sexual debut, and had a higher client volume. Our results call for safer working spaces for FSW and violence prevention interventions for their male clients

Development of Targeted Alpha Particle Therapy for Solid Tumors

Targeted alpha-particle therapy (TAT) aims to selectively deliver radionuclides emitting α-particles (cytotoxic payload) to tumors by chelation to monoclonal antibodies, peptides or small molecules that recognize tumor-associated antigens or cell-surface receptors. Because of the high linear energy transfer (LET) and short range of alpha (α) particles in tissue, cancer cells can be significantly damaged while causing minimal toxicity to surrounding healthy cells. Recent clinical studies have demonstrated the remarkable efficacy of TAT in the treatment of metastatic, castration-resistant prostate cancer. In this comprehensive review, we discuss the current consensus regarding the properties of the α-particle-emitting radionuclides that are potentially relevant for use in the clinic; the TAT-mediated mechanisms responsible for cell death; the different classes of targeting moieties and radiometal chelators available for TAT development; current approaches to calculating radiation dosimetry for TATs; and lead optimization via medicinal chemistry to improve the TAT radiopharmaceutical properties. We have also summarized the use of TATs in pre-clinical and clinical studies to date