CARO was a prospective, multicenter, non-interventional study, registered under the identifier NCT02970747, designed specifically to observe rather than interfere. Instead of assigning patients to strict protocols, researchers followed 359 people with relapsed or refractory multiple myeloma across 69 sites throughout Germany, capturing how carfilzomib-based regimens actually performed in the hands of community oncologists and hospital hematologists. This kind of real-world evidence has become increasingly prized in oncology, because randomized clinical trials, for all their rigor, tend to enroll younger, fitter patients and enforce treatment schedules that bear little resemblance to the compromises forced by age, comorbidities, and everyday life.

The study evaluated three distinct carfilzomib-based combinations that reflect the evolving landscape of myeloma therapy. The first, known as KRd, paired carfilzomib with lenalidomide, an immunomodulatory drug, and dexamethasone, a corticosteroid. The second, Kd, combined carfilzomib with dexamethasone alone. The third and most modern regimen, KdD, added daratumumab, a monoclonal antibody that targets a protein called CD38 on the surface of myeloma cells, to carfilzomib and dexamethasone. By following all three cohorts simultaneously, CARO provided a snapshot of how German physicians deploy these options across a broad and diverse patient population.

Perhaps the most striking finding concerns adherence. Across all three treatment groups, patients remained on carfilzomib therapy at rates exceeding 90 percent, a figure the investigators describe as excellent. In oncology, adherence is often the quiet variable that determines whether a promising drug fulfills its potential, and myeloma patients, who are frequently elderly and burdened by other conditions, are particularly vulnerable to dose reductions, delays, and discontinuation. Sustaining more than nine in ten patients on an intensive proteasome inhibitor regimen suggests that, in routine German practice, carfilzomib-based therapy is manageable in a way that clinical concerns about toxicity had not always guaranteed.

The effectiveness data were equally encouraging and closely mirrored what randomized trials had predicted. Median progression-free survival, the length of time patients live without their disease worsening, reached 17.5 months for those receiving KRd, 13.4 months for those on Kd, and 20.1 months for those treated with the KdD combination that includes daratumumab. These confidence intervals, spanning for example 14.5 to 24.7 months for KRd and 10.9 to 26.6 months for KdD, indicate results statistically consistent with both prior randomized clinical trials and earlier real-world studies of the same regimens. In other words, the benefits observed under idealized trial conditions appear to translate faithfully to ordinary clinics.

Overall survival figures added further weight to the findings. Patients receiving KRd achieved a median overall survival of 38.9 months, while those on Kd reached 24.6 months. Most notably, the median overall survival for the KdD cohort had not yet been reached at the time of analysis, with the lower bound of the confidence interval at 21.9 months, meaning more than half of those patients were still alive when the data were locked. The addition of daratumumab to the carfilzomib and dexamethasone backbone appears to be driving some of the most durable outcomes in the study, consistent with the broader trend of antibody-based immunotherapy reshaping myeloma treatment.

Beyond the survival statistics, CARO also captured something that clinical trials often overlook: how patients actually feel during treatment. Using patient-reported outcome measures, the researchers found that quality of life remained stable throughout the course of therapy, a significant achievement for a population facing a relapsed or refractory cancer. Even more striking, pain parameters improved after six months of treatment. For myeloma patients, whose disease frequently attacks bone and causes debilitating pain, an improvement in this dimension represents a tangible, everyday benefit that no laboratory marker can capture. Stable quality of life combined with reduced pain suggests that the effectiveness of these regimens does not come at the cost of patient wellbeing.

The significance of CARO extends beyond its individual numbers. Real-world evidence studies like this one serve as a critical bridge between the controlled environment of drug registration trials and the heterogeneous reality of clinical practice, where patients may be older, frailer, or have comorbidities that would have excluded them from pivotal studies. By demonstrating that adherence exceeds 90 percent and that effectiveness aligns with trial data across 69 diverse German sites, CARO provides reassurance that the promise of carfilzomib-based therapy holds up outside the spotlight of academic trial centers. This matters for treatment guidelines, for reimbursement decisions, and ultimately for the conversations oncologists have with patients weighing their options after relapse.

The study also reflects the collaborative infrastructure that makes such research possible. CARO was managed and analyzed by iOMEDICO, a research organization based in Freiburg, and received partial financial support from Amgen, the manufacturer of carfilzomib. Importantly, the company had no role in study design, data collection and analysis, interpretation of results, the decision to publish, or preparation of the manuscript, an arrangement intended to safeguard the independence of the findings. The investigator team spanned community practices and university hospitals across Germany, led by researchers including Karin Potthoff of iOMEDICO, with Monika Engelhardt of the University of Freiburg and Wolfgang Knauf of the Centrum für Hämatologie und Onkologie Bethanien in Frankfurt serving as shared senior authors.

For the myeloma community, the final CARO results land at a moment of rapid therapeutic evolution. Proteasome inhibitors like carfilzomib, immunomodulatory agents like lenalidomide, and CD38-directed antibodies like daratumumab now form the backbone of relapsed treatment strategies, and newer options continue to emerge. What CARO demonstrates is that these tools, deployed in the real world by real physicians treating real patients, deliver clinically meaningful outcomes: progression-free survival approaching or exceeding a year and a half in the stronger cohorts, overall survival stretching toward or beyond three years, stable quality of life, and adherence rates that few intensive cancer regimens achieve. As the field moves toward ever more complex combination strategies, studies like CARO provide the ground truth against which future innovations must be measured, and they remind us that a drug’s true value is revealed not in the trial brochure but in the daily lives of the patients who take it.

Subject of Research: Real-world adherence, effectiveness, and quality of life with carfilzomib-based regimens in relapsed/refractory multiple myeloma

Article Title: Final results of the CARO study: real-world adherence, effectiveness and patient-reported quality of life with carfilzomib-based regimens in German patients with relapsed/refractory multiple myeloma

Article References: Potthoff, K., Uhlig, J., Heyde, E. V. D., Losem, C., Nusch, A., Ammon, A., Schöttker, B., Schulz, H., Janssen, J., Welslau, M., Wilop, S., Vannier, C., Hanselmann, J., Serrer, L., Woerner, S. M., Koszinowski, S., Engelhardt, M., & Knauf, W. (2026). Final results of the CARO study: real-world adherence, effectiveness and patient-reported quality of life with carfilzomib-based regimens in German patients with relapsed/refractory multiple myeloma. Annals of Hematology. https://doi.org/10.1007/s00277-026-07302-8

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07302-8

Keywords: multiple myeloma, carfilzomib, KRd, daratumumab, real-world evidence, treatment adherence, progression-free survival, overall survival, quality of life, relapsed refractory myeloma, proteasome inhibitor, Germany

Bortezomib is not a new molecule. The drug, best known for its role in treating multiple myeloma and mantle cell lymphoma, works by blocking the proteasome, the cellular machinery that degrades damaged or unwanted proteins. When proteasomal degradation grinds to a halt, misfolded proteins accumulate, stress pathways ignite and cells that cannot cope are pushed into programmed death. Earlier clinical and laboratory observations had suggested that bortezomib has activity against CTCL, but the molecular wiring behind that activity had never been fully mapped. The research team, led by Kirti S. Prabhu and Shahab Uddin, set out to answer two linked questions: does bortezomib modulate SKP2-associated cell-cycle regulation in CTCL cells, and can it be combined effectively with the platinum chemotherapy drug cisplatin?

To do this, the investigators used two well-characterized human CTCL cell lines, H9 and HH, exposing them to escalating concentrations of bortezomib and measuring viability with cell counting assays, then probing the consequences with fluorescence imaging and flow cytometry. The drug proved remarkably potent. The 24-hour concentration that killed half the cells, the IC50, was just 5.25 nanomolar in H9 cells and an even lower 1.82 nanomolar in HH cells. Values in the low nanomolar range are notable because they sit comfortably within concentrations achievable in clinical practice, lending translational weight to the laboratory findings. The team then asked what kind of death the cells were dying, and the answer was unambiguous: apoptosis, the orderly suicide program that cancer cells often manage to evade.

The apoptotic signature emerged at several levels simultaneously. Flow cytometry revealed a rising sub-G0/G1 population, a classic hallmark of cells with fragmented DNA, alongside an increase in Annexin V-positive cells, which flag the externalization of phosphatidylserine, an early molecular signal of apoptosis. Immunoblotting showed activation of the caspase cascade, the proteolytic machinery that executes cell death: caspase-8, caspase-9 and caspase-3 were all cleaved into their active forms, and PARP, a DNA repair enzyme that caspase-3 slices as a finishing blow, was cleaved as well. The intrinsic, or mitochondrial, arm of apoptosis was clearly engaged, because the ratio of the pro-death protein Bax to the pro-survival protein Bcl-2 increased, and the mitochondrial membrane potential collapsed, a depolarization event that releases apoptogenic factors from the intermembrane space into the cytosol.

To confirm that this death was truly caspase-dependent, the researchers pre-treated cells with z-VAD-FMK, a broad-spectrum inhibitor that shuts down all caspases. The inhibitor significantly blunted bortezomib-induced apoptosis, demonstrating that the caspase cascade is a functional component of the drug’s cytotoxicity rather than a bystander effect. That finding matters because it anchors bortezomib’s action in a defined, druggable death pathway, one that can be monitored and potentially amplified by rational drug combinations.

Perhaps the most mechanistically revealing part of the study concerns reactive oxygen species, or ROS. Bortezomib treatment increased both cellular and mitochondrial ROS and simultaneously depleted intracellular glutathione, the cell’s principal endogenous antioxidant buffer. This double hit, more oxidants and less antioxidant capacity, creates a state of oxidative stress that damages mitochondrial membranes and feeds the apoptotic circuit. The causal contribution of ROS was tested with N-acetyl-L-cysteine, a glutathione-replenishing antioxidant. When NAC was present, bortezomib’s disruption of the cell cycle, its induction of apoptosis and its activation of caspases were all partially reduced. In other words, oxidative stress is not the whole story, but it is a genuine upstream driver of the cytotoxic program, and the partial rescue suggests that bortezomib kills CTCL cells through converging ROS-dependent and ROS-independent routes.

The study also connected bortezomib’s effects to cell-cycle control, an area where CTCL cells are particularly vulnerable. The team observed a marked suppression of SKP2, S-phase kinase-associated protein 2, an E3 ubiquitin ligase component famous for tagging the cyclin-dependent kinase inhibitors p21 and p27 for destruction. When SKP2 falls, its targets accumulate, and that is exactly what the researchers documented: levels of p21 and p27 rose while the cyclin-dependent kinases CDK4 and CDK6, which drive cells through the G1 checkpoint, declined. This SKP2-p21/p27 axis functions as a brake on proliferation, and bortezomib effectively re-engages that brake. Because SKP2 is an oncogenic driver in many lymphoid malignancies, its suppression offers a candidate pharmacodynamic vulnerability, a measurable molecular endpoint that clinicians could track to confirm that the drug is hitting its intended target in patients.

Combination therapy was the final piece of the puzzle. Platinum-based agents such as cisplatin are mainstays of oncology, but their use in CTCL is limited by toxicity and modest durable benefit. Using the Chou-Talalay method, a widely accepted mathematical framework for quantifying drug interactions through the combination index, the researchers tested whether bortezomib and cisplatin act cooperatively. At selected dose pairings, bortezomib enhanced cisplatin-induced loss of viability and apoptosis, and the interaction was strongly synergistic at 5 nanomolar bortezomib combined with 10 micromolar cisplatin. Synergy means the combination kills more cells than the sum of the two drugs acting alone, a property that could, in principle, allow lower doses of each agent and a narrower toxicity profile. The mechanistic logic is plausible: bortezomib’s ROS generation and caspase priming may lower the apoptotic threshold that cisplatin-induced DNA damage must cross to trigger cell death.

The authors are careful to frame these results as a foundation rather than a clinical verdict. All of the experiments were performed in established cell lines, and the study’s own conclusions call for validation in primary CTCL samples from patients and in in vivo models before the strategy can move toward the clinic. That caveat is standard and appropriate, yet the work still carries real significance. It converts a clinical observation, that bortezomib has activity in CTCL, into a mechanistic account involving ROS accumulation, glutathione depletion, mitochondrial depolarization, caspase activation and SKP2 pathway suppression, and it nominates a specific synergistic drug pairing for further testing. For a disease with limited durable options in its advanced stages, that combination of mechanistic depth and translational direction is exactly the kind of progress that translational medicine aims to deliver, and it gives CTCL researchers a clear set of molecular signposts to follow in the next phase of preclinical and clinical evaluation.

Subject of Research: Proteasome inhibitor bortezomib-induced ROS-dependent mitochondrial apoptosis and SKP2 signaling suppression in cutaneous T-cell lymphoma cells

Article Title: Bortezomib induces ROS-dependent mitochondrial apoptosis and suppresses SKP2 signaling in cutaneous T-cell lymphoma cells

Article References: Bortezomib induces ROS-dependent mitochondrial apoptosis and suppresses SKP2 signaling in cutaneous T-cell lymphoma cells. (n.d.). https://doi.org/10.1186/s12967-026-09039-4

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09039-4

Keywords: cutaneous T-cell lymphoma, bortezomib, SKP2, reactive oxygen species, mitochondrial apoptosis, caspases, p21, p27, cisplatin, proteasome inhibitor, glutathione, drug synergy