Anti-apoptotic Bcl-2 family proteins are often highly expressed in chemotherapy-resistant cancers and impair mitochondrial outer membrane permeabilisation (MOMP), a key requirement for caspase activation via the intrinsic apoptosis pathway. Interestingly, while Bcl-2 overexpression in HeLa cervical cancer cells abrogated caspase processing in response to intrinsic apoptosis induction by staurosporine, tunicamycin or etoposide, residual caspase processing was observed following proteasome inhibition by bortezomib, epoxomicin or MG-132. Similar responses were found in Bcl-2 overexpressing H460 NSCLC cells and Bax/Bak-deficient mouse embyronic fibroblasts. Mild caspase processing resulted in low DEVDase activities, which were MOMP independent and persisted for long periods without evoking immediate cell death. Surprisingly, depletion of caspase-3 and experiments in caspase-7-depleted MCF-7-Bcl-2 cells indicated that the DEVDase activity did not originate from effector caspases. Instead, FADD-dependent caspase-8 activation was the major contributor to the slow, incomplete substrate cleavage. Casapse-8 activation was independent of death ligands but required the induction of autophagy and the presence of Atg5. Depletion of XIAP or addition of XIAP-antagonizing peptides resulted in a switch towards efficient apoptosis execution, suggesting that the requirement for MOMP was bypassed by activating the caspase-8/caspase-3 axis. Combination treatments of proteasome inhibitors and XIAP antagonists therefore represent a promising strategy to eliminate highly resistant cancer cells which overexpress anti-apoptotic Bcl-2 family members.

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ImportanceRetinal vein occlusion is the second most common retinal vascular disease. Bevacizumab was demonstrated in the Study of Comparative Treatments for Retinal Vein Occlusion 2 (SCORE2) to be noninferior to aflibercept with respect to visual acuity in study participants with macular edema due to central retinal vein occlusion (CRVO) or hemiretinal vein occlusion (HRVO) following 6 months of therapy. In this study, the cost-utility of bevacizumab vs aflibercept for treatment of CRVO is evaluated.ObjectiveTo investigate the relative cost-effectiveness of bevacizumab vs aflibercept for treatment of macular edema associated with CRVO or HRVO.Design, Setting, and ParticipantsThis economic evaluation study used a microsimulation cohort of patients with clinical and demographic characteristics similar to those of SCORE2 participants and a Markov process. Parameters were estimated and validated using a split-sample approach of the SCORE2 population. The simulated cohort included 5000 patients who were evaluated 100 times, each with a different set of characteristics randomly selected based on the SCORE2 trial. SCORE2 data were collected from September 2014 October 2019, and data were analyzed from October 2019 to July 2021.InterventionsBevacizumab (followed by aflibercept among patients with a protocol-defined poor or marginal response to bevacizumab at month 6) vs aflibercept (followed by a dexamethasone implant among patients with a protocol-defined poor or marginal response to aflibercept at month 6).Main Outcomes and MeasuresIncremental cost-utility ratio.ResultsThe simulation demonstrated that patients treated with aflibercept will have an expected cost $18 127 greater than those treated with bevacizumab in the year following initiation. When coupled with the lack of clinical superiority over bevacizumab (ie, patients treated with bevacizumab had a gain over aflibercept in visual acuity letter score of 4 in the treated eye and 2 in the fellow eye), these results demonstrate that first-line treatment with bevacizumab dominated aflibercept in the simulated cohort of SCORE2 participants. At current price levels, aflibercept would be considered the preferred cost-effective option only if treatment restored the patient to nearly perfect health.Conclusions and RelevanceWhile there will be some patients with CRVO-associated or HRVO-associated macular edema who will benefit from first-line treatment with aflibercept rather than bevacizumab, given the minimal differences in visual acuity outcomes and large cost differences for bevacizumab vs aflibercept, first-line treatment with bevacizumab is cost-effective for this condition.

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