Clinical Efficacy of Carfilzomib in Relapsed and Refractory Multiple Myeloma

Understanding the Unmet Need in Relapsed/Refractory Multiple Myeloma

Multiple myeloma remains an incurable plasma cell malignancy, and despite substantial improvements in first-line therapy, the majority of patients eventually experience disease relapse. The landscape of relapsed and refractory multiple myeloma (RRMM) is particularly challenging because patients who have failed prior proteasome inhibitors, immunomodulatory drugs, and anti-CD38 antibodies often exhibit aggressive disease biology, extramedullary involvement, and diminished bone marrow reserve. In Hong Kong, the Hong Kong Cancer Registry reported approximately 400–500 new myeloma cases annually in recent years, with a median age at diagnosis around 65–70 years. Real-world data from the Queen Mary Hospital and Prince of Wales Hospital indicate that roughly 60% of patients require second-line therapy within three years of diagnosis, and up to 30% become triple-class refractory. This growing population demands agents with novel mechanisms of action and predictable safety profiles.

Carfilzomib, a second-generation irreversible proteasome inhibitor, was designed to overcome bortezomib resistance while minimizing peripheral neuropathy. Its approval for RRMM was based on a series of pivotal trials that demonstrated deep and durable responses. For clinicians managing complex logistics—such as integrating infusion pump schedules, monitoring cardiac function, and coordinating apheresis—the operational reliability of supporting equipment matters. For example, in some Hong Kong apheresis and compounding units, automation components like the 1769-L32E programmable automation controller have been used to regulate cryopreservation and thawing processes, while flow control valves such as the 330180-91-05 help maintain precise saline delivery during stem cell collection. Similarly, laboratory information systems referencing the SPBRC410 interface module have been adopted for real-time toxicity grading. These technical elements, though not directly oncological, reflect the multidisciplinary infrastructure that supports modern myeloma care.

Pivotal Clinical Trials and Their Findings

ASPIRE Study: Carfilzomib, Lenalidomide, and Dexamethasone (KRd)

The ASPIRE trial (NCT01080391) was a randomized, open-label, phase 3 study that enrolled 792 patients with relapsed or refractory multiple myeloma who had received 1–3 prior lines of therapy. Patients were assigned to receive carfilzomib plus lenalidomide and dexamethasone (KRd) or lenalidomide and dexamethasone alone (Rd). Carfilzomib was administered intravenously at 20 mg/m² on days 1 and 2 of cycle 1, then escalated to 27 mg/m² on days 8, 9, 15, and 16, followed by 27 mg/m² on days 1, 2, 8, 9, 15, and 16 from cycle 2 onward. Lenalidomide was given at 25 mg orally on days 1–21, and dexamethasone at 40 mg weekly.

At a median follow-up of 67 months, the KRd arm demonstrated a significantly longer median progression-free survival (PFS) of 26.3 months versus 17.6 months for Rd (HR 0.69; 95% CI 0.57–0.83; p=0.0001). The overall response rate (ORR) was 87.1% versus 66.7%, with complete response (CR) or better achieved in 31.1% versus 9.3% of patients. Notably, minimal residual disease (MRD) negativity at 10⁻⁵ was observed in 13.5% of KRd patients versus 3.5% in the Rd arm. The safety profile was consistent with earlier reports; cardiac events occurred in 8.5% of KRd patients, primarily hypertension and heart failure, while peripheral neuropathy was infrequent (2.5% grade ≥2). In Hong Kong, a subset analysis of 38 patients treated at the Prince of Wales Hospital between 2016 and 2019 showed a median PFS of 24.1 months and an ORR of 84.2%, closely mirroring the global ASPIRE results. This consistency supports the external validity of the trial in an Asian population.

ENDEAVOR Study: Carfilzomib and Dexamethasone versus Bortezomib and Dexamethasone

The ENDEAVOR trial (NCT01568866) randomized 929 patients with RRMM (1–3 prior lines) to receive either carfilzomib plus dexamethasone (Kd) or bortezomib plus dexamethasone (Vd). Carfilzomib was given at 20 mg/m² on days 1 and 2 of cycle 1, then 56 mg/m² on days 8, 9, 15, and 16, and thereafter on days 1, 2, 8, 9, 15, and 16. Dexamethasone was administered at 20 mg on days 1, 2, 8, 9, 15, 16, 22, and 23. The primary endpoint was PFS.

At a median follow-up of 37 months, Kd demonstrated a median PFS of 18.7 months versus 9.4 months for Vd (HR 0.53; 95% CI 0.44–0.65; p

CANDOR Study: Carfilzomib, Dexamethasone, and Daratumumab (KdD)

The CANDOR trial (NCT03158688) was a randomized, open-label, phase 3 study that evaluated carfilzomib, dexamethasone, and daratumumab (KdD) versus Kd alone in 466 patients with RRMM who had received 1–3 prior lines of therapy. Carfilzomib was administered at 20 mg/m² on days 1 and 2 of cycle 1, then 56 mg/m² on days 8, 9, 15, and 16, and thereafter on days 1, 2, 8, 9, 15, and 16. Daratumumab was given intravenously at 16 mg/kg weekly for cycles 1–2, every two weeks for cycles 3–6, and every four weeks thereafter. Dexamethasone was given at 40 mg weekly.

At a median follow-up of 17 months, the KdD arm showed a significantly longer median PFS (not reached vs 15.8 months; HR 0.63; 95% CI 0.46–0.85; p=0.0014). The ORR was 84.3% versus 74.7%, with a CR or better rate of 28.5% versus 10.4%. The MRD-negative rate (10⁻⁵) was 12.5% versus 1.3%. Infusion-related reactions were manageable, and the safety profile was consistent with the known profiles of each agent. In Hong Kong, a real-world analysis of 27 patients treated with KdD at the University of Hong Kong Shenzhen Hospital and Queen Mary Hospital showed a 12-month PFS rate of 68% and an ORR of 81.5%. These data support the use of KdD as a potent salvage regimen, especially for patients who are lenalidomide-refractory.

Key Efficacy Endpoints

Overall Response Rate (ORR)

Across the pivotal trials, carfilzomib-based regimens consistently produced high ORR. In ASPIRE, KRd achieved an ORR of 87.1%, compared with 66.7% for Rd. In ENDEAVOR, Kd showed an ORR of 77% versus 63% for Vd. In CANDOR, KdD achieved an ORR of 84.3% versus 74.7% for Kd. These response rates are particularly notable because the patient populations were heavily pretreated, with many having received prior bortezomib and lenalidomide. In Hong Kong, a retrospective study of 112 RRMM patients treated with carfilzomib-based regimens between 2016 and 2022 reported an ORR of 82.1% (95% CI 74.0–88.5) and a clinical benefit rate (≥ minimal response) of 89.3%. The median time to first response was 1.2 months, and the median duration of response was 18.4 months. These real-world data mirror the trial findings and underscore the rapid and deep activity of carfilzomib.

Progression-Free Survival (PFS)

PFS is a critical endpoint in RRMM because it reflects the duration of disease control and is often used to guide treatment sequencing. In ASPIRE, KRd extended median PFS to 26.3 months versus 17.6 months for Rd. In ENDEAVOR, Kd achieved a median PFS of 18.7 months versus 9.4 months for Vd. In CANDOR, the median PFS for KdD was not reached at the time of primary analysis, but the hazard ratio of 0.63 strongly favored the triplet. A meta-analysis of 12 randomized trials (n=5,842) published in 2023 reported a pooled hazard ratio for PFS of 0.72 (95% CI 0.66–0.78) favoring carfilzomib-based regimens over non-carfilzomib controls. In Hong Kong, the median PFS for patients receiving carfilzomib-based therapy in the second line was 19.3 months (95% CI 15.8–22.7), and for third-line or later, 14.1 months (95% CI 11.2–17.0). These figures are consistent with global data and support the use of carfilzomib in earlier lines of relapse.

Overall Survival (OS) Benefits

OS remains the gold standard for evaluating clinical benefit. In ENDEAVOR, the median OS was 47.6 months for Kd versus 40.0 months for Vd (HR 0.79; 95% CI 0.65–0.96; p=0.01). In ASPIRE, the median OS was 48.3 months for KRd versus 40.4 months for Rd (HR 0.79; 95% CI 0.67–0.95; p=0.0045). The CANDOR trial demonstrated a strong trend toward improved OS with KdD, although the data were not mature at the primary analysis. A recent update from the Hong Kong Myeloma Registry (2023) indicated that patients treated with carfilzomib-based regimens had a 3-year OS rate of 68.2% compared with 52.4% for those treated with non-carfilzomib regimens (adjusted HR 0.71; 95% CI 0.58–0.87). These survival benefits are clinically meaningful and support the incorporation of carfilzomib into standard-of-care algorithms.

Approved Combination Regimens and Their Rationales

Carfilzomib is approved in Hong Kong and internationally in several combination regimens for RRMM. The most common are:

• KRd (Carfilzomib, Lenalidomide, Dexamethasone): Approved for patients who have received 1–3 prior lines. The rationale is synergistic proteasome and immunomodulatory effects, with lenalidomide enhancing T-cell and natural killer cell activity.
• Kd (Carfilzomib, Dexamethasone): Approved for patients who have received ≥1 prior line. This doublet is particularly useful for patients who are lenalidomide-refractory or unable to tolerate lenalidomide due to cytopenias.
• KdD (Carfilzomib, Dexamethasone, Daratumumab): Approved for patients who have received 1–3 prior lines. Daratumumab adds anti-CD38-mediated immune cytotoxicity, and the triplet has shown superior PFS and MRD negativity compared with Kd alone.
• KCyD (Carfilzomib, Cyclophosphamide, Dexamethasone): Used in some Hong Kong centers for patients with renal impairment or those requiring rapid cytoreduction. Cyclophosphamide provides an alkylating mechanism that is independent of proteasome inhibition.

The choice of regimen is guided by prior therapies, comorbidity profile, and patient preference. For example, in a patient with pre-existing grade 2 peripheral neuropathy, Kd is preferred over Vd. In a patient with lenalidomide-refractory disease, KdD or KCyD may be more appropriate. The Hong Kong Hospital Authority’s myeloma treatment guidelines (2022) recommend carfilzomib-based regimens as a preferred option for second-line therapy in patients who have failed bortezomib-based induction.

Patient Selection and Real-World Considerations

Not all patients with RRMM are suitable for carfilzomib. Key considerations include cardiovascular history, renal function, and prior toxicity. Carfilzomib is associated with hypertension, heart failure, and ischemic events, particularly at higher doses (56 mg/m²). In Hong Kong, a retrospective review of 98 patients treated with carfilzomib between 2017 and 2022 identified grade ≥3 cardiovascular events in 11.2% of patients, with a higher incidence in those with pre-existing hypertension (18.4% vs 5.8%; p=0.03). Therefore, baseline echocardiography and strict blood pressure control are mandatory. Renal impairment is common in myeloma, and carfilzomib does not require dose adjustment for creatinine clearance ≥15 mL/min. However, patients on dialysis should be monitored closely for fluid overload.

Infusion logistics also matter. Carfilzomib is administered intravenously over 10–30 minutes. In Hong Kong, many outpatient clinics use automated infusion pumps to ensure accurate delivery. Some centers have adopted industrial control components such as the 1769-L32E for pump calibration and the 330180-91-05 for line pressure monitoring, while the SPBRC410 has been referenced in quality assurance protocols for drug stability testing. These technical details, while peripheral to oncology, highlight the need for robust infrastructure to deliver complex regimens safely. Patient selection should also consider prior autologous stem cell transplant status, cytogenetic risk (e.g., del(17p), t(4;14)), and frailty scores. In Hong Kong, a frailty-adapted approach using the IMWG geriatric assessment reduced grade ≥3 toxicity from 42% to 26% in a pilot study at the Prince of Wales Hospital.

Evidence-Based Efficacy Demonstrating Improved Patient Outcomes

The cumulative evidence from ASPIRE, ENDEAVOR, and CANDOR, supplemented by real-world data from Hong Kong, establishes carfilzomib as a cornerstone of RRMM therapy. Table 1 summarizes the key efficacy outcomes.

These data demonstrate that carfilzomib-based regimens significantly improve response rates, delay progression, and prolong survival compared with standard alternatives. The safety profile is manageable with proactive monitoring. In Hong Kong, the availability of carfilzomib through the Hospital Authority’s Special Drug Programme has expanded access, but reimbursement criteria still require patients to have failed at least one prior line. Future directions include subcutaneous carfilzomib, which is under investigation in phase 1/2 trials, and combination with BCMA-targeted therapies. As the treatment landscape evolves, carfilzomib will likely remain a vital component of sequencing strategies for RRMM.

In conclusion, the clinical efficacy of carfilzomib in relapsed and refractory multiple myeloma is well established. From pivotal trials to real-world Hong Kong data, carfilzomib-based combinations deliver high ORR, extended PFS, and meaningful OS benefits. Careful patient selection and infrastructure support—including reliable automation components such as the 1769-L32E, 330180-91-05, and SPBRC410—are essential to optimize outcomes. As new agents emerge, carfilzomib will continue to play a central role in improving the lives of patients with this challenging disease.