Efficacy and safety of daratumumab with ixazomib and dexamethasone in lenalidomide‐exposed patients after one prior line of therapy: Final results of the phase 2 study DARIA

The use of lenalidomide in frontline therapy for patients with newly diagnosed multiple myeloma (MM) has increased the number of those who become refractory to lenalidomide at second line. In this context, we assessed the efficacy of daratumumab in combination with ixazomib and dexamethasone (Dara‐Ixa‐dex) in the prospective phase 2 study DARIA. Eligible patients had relapsed/refractory MM (RRMM) after one prior line with a lenalidomide‐based regimen. The primary endpoint was overall response rate (ORR). Secondary endpoints included survival outcomes, safety and changes in biomarkers of bone metabolism. Overall, 50 patients were enrolled (median age 69 years, 56% males). 32 (64%) patients were refractory to lenalidomide, and 17 (34%) had undergone autologous transplant. The ORR was 64% (n = 32); whereas 17 (34%) had a very good partial response or better. The median time to first response was 1.0 month. After a median follow‐up of 23.4 months, the median PFS and OS were 8.1 and 39.2 months, respectively. Furthermore, significant changes in markers of bone metabolism became evident as early as at 6 months on treatment. Regarding safety, 21 (42%) patients had ≥1 grade 3/4 adverse event (AE); the most common was thrombocytopenia (n = 9, 18%). 14 (28%) patients had ≥1 serious AE (SAE), the most common being acute kidney injury and pneumonia (n = 2, each). Four patients died due to infections. In conclusion, second‐line treatment with Dara‐Ixa‐dex in patients with RRMM pre‐treated with a lenalidomide‐based regimen resulted in rapid responses along with a favorable effect on bone metabolism.

were refractory to lenalidomide, and 17 (34%) had undergone autologous transplant.The ORR was 64% (n = 32); whereas 17 (34%) had a very good partial response or better.The median time to first response was 1.0 month.After a median follow-up of 23.4 months, the median PFS and OS were 8.1 and 39.2 months, respectively.Furthermore, significant changes in markers of bone metabolism became evident as early as at 6 months on treatment.Regarding safety, 21 (42%) patients had ≥1 grade 3/4 adverse event (AE); the most common was thrombocytopenia (n = 9, 18%).14 (28%) patients had ≥1 serious AE (SAE), the most common being acute kidney injury and pneumonia (n = 2, each).Four patients died due to infections.In conclusion, second-line treatment with Dara-Ixa-dex in patients with RRMM pre-treated with a lenalidomide-based regimen resulted in rapid responses along with a favorable effect on bone metabolism.

| INTRODUCTION
Lenalidomide is an immunomodulatory drug that has been wellestablished as an essential backbone in the upfront treatment of patients with newly diagnosed multiple myeloma (NDMM).
Lenalidomide-based triplet combinations have become the standard of care for both fit patients who are eligible for autologous stem cell transplantation (ASCT) and unfit, elderly patients. 1Furthermore, lenalidomide is currently the only approved drug to be used as a maintenance treatment following ASCT, 2 whereas it is usually administered continuously in elderly patients.Therefore, the extensive use of lenalidomide in frontline therapy for patients with NDMM has increased the number of those who become refractory to lenalidomide at second line. 3This includes those patients who have documented disease progression while receiving lenalidomide or within 60 days since the last dose of lenalidomide. 4ratumumab is an anti-CD38 monoclonal antibody that has been also integrated in the therapeutic algorithm of both NDMM and relapsed/refractory multiple myeloma (RRMM). 1,57][8] The convenience and tolerability of the therapy have also been enhanced by the approval of daratumumab as a subcutaneous form, which has decreased infusion times and the possibility of infusion-related adverse events. 9Clinical trials, including the PLEIADES and the COLUMBA studies, have demonstrated the non-inferiority of subcutaneous in comparison to intravenous daratumumab in terms of efficacy. 10,11In the clinical practice, when daratumumab is not used in the first line due to accessibility reasons, patient/physician choice or costeffectiveness, 12 it becomes an integral part of the most effective triplet regimens used in the second line in combination with a proteasome inhibitor (e.g., carfilzomib) 13 or an immunomodulatory drug (eg pomalidomide) 14 along with dexamethasone.However, carfilzomib is administered intravenously twice weekly and pomalidomide is given orally once daily.A retrospective study on 256 patients with MM who progressed on lenalidomide maintenance showed that second-line treatment with daratumumabbased regimens and salvage ASCT had the best survival outcomes. 3azomib is a proteasome inhibitor that has been approved in combination with lenalidomide and dexamethasone for the treatment of patients with RRMM with a favorable efficacy and safety profile according to clinical trial and real-world data. 15,16It is administered orally once weekly, and, thus, it is convenient for the patient to comply with the therapeutic regimen, especially in the relapsed disease setting that necessitates long-term, continuous treatment. 16king all the above into consideration, we assessed the efficacy of daratumumab in combination with ixazomib and dexamethasone (Dara-Ixa-dex) in the second-line treatment of patients with MM who had received a lenalidomide-based induction.

| Patient selection
Eligible adult patients had been diagnosed with RRMM according to the International Myeloma Working Group (IMWG) criteria 17 and they had received only one prior line of treatment with a lenalidomide-based regimen.All patients should have measurable disease in serum (M-paraprotein, free light chains) and/or urine (U-paraprotein) and a Karnofsky Performance Status (KPS) score of at least 70%.Patients who had received previous treatment with an anti-CD38 monoclonal antibody or with ixazomib were excluded.Patients should have not received any anti-myeloma treatment within 2 weeks or 5 pharmacokinetic half-lives of the treatment prior to initiation of the study regimen, whereas no ASCT or allogeneic stem cell transplant was permitted within 12 weeks before the first dose of the study regimen.All patients provided written informed consent before enrolment in the study.

| Study outcomes
The primary endpoint was overall response rate (ORR), defined as the proportion of patients who achieved a best response of partial response (PR) or better using the IMWG consensus criteria. 4Secondary endpoints included the toxicity profile of Dara-Ixa-dex, progression-free survival (PFS), overall survival (OS), duration of response (DOR), time to progression (TTP), time to next treatment (TtNT), and the effects of the Dara-Ixa-dex combination on serum markers of bone metabolism including C-terminal telopeptide of type 1 collagen (CTX), tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), procollagen type I N-terminal propeptide (PINP), bone-specific alkaline phosphatase (bALP), osteocalcin (OC), dickkopf-1 (Dkk-1), sclerostin (SOST), receptor activator of nuclear factor kappa-Β ligand (RANKL), and osteoprotegerin (OPG).Biomarkers of bone metabolism were evaluated at baseline and every 3 months until disease progression or end of study treatment.The measurements were based on enzyme-linked immunosorbent assays (ELISA), as described previously in detail. 18

| Statistical analysis
The sample size of the study was estimated according to the two-stage Simon phase II design, with early stopping rules.More specifically, an ORR of 60% was considered not promising, the probability of type I (α) error was set at 0.05 and type II (β) error at 0.20.In the first stage of the two-stage Simon phase II design, 11 patients were estimated to be accrued.If 7/11 or less responses would be observed in this stage, the trial would be stopped for futility.The study successfully completed the stage I and continued to stage II.The remaining patients were accrued in the second stage.With this design, an adequate sample size was estimated at 50 patients, assuming a 10%-15% lost to follow-up rate.
Summary statistics based on frequency tables were used for categorical variables.For continuous variables, descriptive statistics (number of patients, mean, median, standard deviation, Q1, Q3, min, and max values) were used.The Kaplan-Meier method was applied for all time to event analyses.PFS, OS, TTP, TtNT were calculated beginning from the date of first study dose (cycle 1 day 1) to disease progression or death from any cause (PFS), death from any cause (OS), disease progression (TTP), initiation of next line of treatment or death from any cause (TtNT).
DOR was calculated from the date of first confirmed response (at least PR) until the date of documented disease progression.Mixed Models for Repeated Measures (MMRM) were employed for the analysis of the Biomarkers.Log-transformation was applied for all the biomarkers which were treated as dependent variables while time was used as fixed factor.
Likelihood ratio tests were used for the random effects selection and Kenward-Roger estimation was the methodology for the degrees of freedom.All analyses were performed in the Full Analysis Set (FAS) which included all patients that received at least one dose of the study treatment.All statistical analyses and generation of tables and patient data listings were performed using SAS ® statistical analysis software (v.9.4, SAS Institute, Cary, NC, USA).

| Baseline patient and treatment characteristics
Overall, 50 patients were enrolled in the study.The median age was 69 years (range 50-89 years), whereas 56% (n = 28) were males.At screening, 38 patients (76%) had a KPS score of at least 90%, and the majority of the participants were revised international staging system (R-ISS) stage I and II (n = 47, 94%).All patients had received one prior line of treatment, whereas 80% (n = 40) had been exposed to a proteasome inhibitor.Thirty-two patients (64%) were refractory to lenalidomide, and 17 (34%) had undergone prior ASCT.Baseline patient characteristics are provided in Table 1.
a Missing in one patient.
bisphosphonates (zoledronic acid) along with the study treatment.

| Evaluation of bone metabolism
Regarding biomarkers of bone anabolism, significant percent increases The treatment effect on the absolute values of bone metabolism biomarkers are summarized in Table 2.The use of bisphosphonates did not have a significant effect on the changes in bone markers from baseline over time, however the number in the subgroups is low and these results should be interpretated with caution.
Five patients experienced at least one infusion-related reaction.All were grade 2 and resolved completely; however, one patient experienced grade 4 dyspnea and bronchospasm during an intravenous infusion of daratumumab and the drug was permanently discontinued.
Another patient was diagnosed with lung cancer during the study period and treatment was discontinued.

| DISCUSSION
In this study, patients with RRMM who had previously received a lenalidomide-based regimen were treated with Dara-Ixa-dex as second-line therapy.The results showed a rapid response in 64% of the patients, whereas one third had deep responses (VGPR or better).
The median PFS in this patient population was 8 months, while the median duration of response was almost 1.5 years.The prolonged OS may be attributed to subsequent lines of therapy with novel agents.
The results of another phase 2 study evaluating the combination of Dara-Ixa-dex in patients with RRMM (ClinicalTrials.govidentifier NCT03439293) has been previously reported as a conference abstract. 19The dosing scheme was similar to our study; however, there was no distinct maintenance phase and dexamethasone was administered continuously.Furthermore, the study included patients with one to three prior lines of treatment, in contrast to the DARIA study that enrolled only patients with one prior therapy.However, most of the patients had received one (59%) or two (26%) prior lines of treatment.Among 59 enrolled patients in the NCT03439293 study, the ORR reached 66%, whereas 32.2% of the patients had VGPR or better, which is in line with our results.After a median follow up of 31.6 months, the median PFS was 16.8 months (95% CI: 10.1-23.7) and the median TTP was 21.1 months (95% CI: 10.2-27.9). 19The prolonged median PFS and TTP compared to the DARIA study may be attributed, at least partially, to the higher proportion of patients refractory to lenalidomide in DARIA (64%) compared to the NCT03439293 study (34%).Both DARIA and NCT03439293 studies had the response rate as a primary endpoint.A systematic analysis on   .
a Estimated using a linear repeated measures model with biomarker log-transformed values at each timepoint as the depended variable and visit (i.e., cycle) as fixed effect.
clinical trials reporting the outcomes of patients with RRMM showed that the depth of response, and especially the VGPR or better rate, can be a surrogate endpoint for PFS. 20More robust survival endpoints such as PFS and OS would require a more prolonged follow-up in larger patient cohorts.
Triplet combinations are the mainstay of treatment at the first relapse of patients with RRMM. 21Several different regimens, most of them including an anti-CD38 monoclonal antibody, have shown superiority over doublet regimens in the relapsed/refractory setting. 22Patients who are refractory to lenalidomide at first line have multiple options including daratumumab with carfilzomib and dexamethasone (DKd), 13,23,24 isatuximab with carfilzomib and dexamethasone (IKd), 25,26 daratumumab with bortezomib and dexamethasone (DVd), 27,28 selinexor with bortezomib and dexamethasone (SVd), 29 and pomalidomide with bortezomib and dexamethasone (PVd). 30The choice of treatment is based on several patient-and disease-related factors. 1 A subset of patients may be ineligible for receiving triplet combinations due to frailty, comorbidities, ongoing toxicity from prior treatment or accessibility issues.Persisting peripheral neuropathy may preclude the longterm administration of bortezomib, 31 whereas cardiovascular disease, such as hypertension, heart failure and ischemic heart disease, may complicate the use of carfilzomib. 32,33Patient adherence to selinexor may be challenging mainly due to gastrointestinal toxicity, fatigue, decreased appetite and weight loss. 34Although some patients may derive benefit from monotherapy with daratumumab or isatuximab, the survival outcomes are often suboptimal 18,[35][36][37] ; therefore, triplets should be preferred in all patients. 1In addition to the above, novel immunotherapies including chimeric antigen receptor (CAR) T-cells and bispecific antibodies have shown significant activity for patients with RRMM and they are currently under investigation in earlier lines of therapy.Interestingly, ciltacabtagene autoleucel was superior to any standard of care in the CARTITUDE-4 study both in the whole cohort of lenalidomiderefractory patients with 1 to 3 prior lines and among the subset of patients with one prior line of treatment with an HR of 0.35 (95% CI: 0.19-0.66). 38However, availability and patient accessibility to CAR T-cell therapy remains a challenge.
For patients who have received a median of 2-3 prior lines of therapy, key treatment choices include also combinations of anti-CD38 monoclonal antibodies with pomalidomide and dexamethasone.
The phase 3 APOLLO study showed an ORR of 69% for the combination of daratumumab with pomalidomide and dexamethasone (DPd), 39 whereas the phase 3 ICARIA study showed an ORR of 60% for the combination of isatuximab with pomalidomide and dexamethasone (IPd) 40 in patients with a median of 2 and 3 prior lines of treatment, respectively.0][41] Both studies had a high percentage of lenalidomide refractory patients (79% in the APOLLO and 94% in the ICARIA study) and anti-CD38-based triplet combinations were superior to Pd in these subgroups, as well. 39,40Nevertheless, the median PFS with DPd was 9.9 months among lenalidomide-refractory patients. 39though cross-trial comparisons should be made with caution, taking also into consideration that APOLLO and ICARIA studies had a higher proportion of lenalidomide-refractory patients and a more heavily pretreated population compared to the DARIA study, the outcomes seem more favorable with DPd/IPd compared to Dara-Ixa-dex.However, Dara-Ixa-dex remains a suitable option in case of patient intolerance to IMiDs including pomalidomide.
Ixazomib-based combinations have shown important efficacy in patients with RRMM without major safety concerns.Ixazomib in combination with dexamethasone has shown similar efficacy and fewer severe (grade 3 or higher) treatment-emergent adverse events compared to the combination of pomalidomide with dexamethasone in a phase 2 trial including in lenalidomide-refractory patients with RRMM. 42Ixazomib in combination with lenalidomide and dexamethasone (IRd) has been approved based on the results of the TOURMALINE-MM1 clinical trial that showed a statistically significant PFS benefit over Rd. 15 However, a significant OS benefit was not observed in the final analysis, possibly due to the type of subsequent lines of therapies including an inferior proportion of patients in the IRd group who received daratumumab-based compared with the Rd group. 435][46][47] Interestingly, pharmacoeconomic analyses both in the United States of America and in Europe have suggested that all-oral IRd regimen is among the least expensive approved triplet regimens for patients with RRMM. 48,49e combination of Dara-Ixa-dex has been also evaluated in the first-line treatment of patients with NDMM who are not fit for ASCT. 50,51The Hovon 143 phase 2 clinical trial included 65 frail patients according to the IMWG frailty index 52 who received 9 cycles of Dara-Ixa-dex followed by Dara-Ixa maintenance for up to 2 years. 50e ORR was 78%, whereas the median PFS was 13.8 months and OS rate at 12 months was 78%.Patients who were characterized as frail exclusively due to age more than 80 years had better outcomes compared to patients who had also comorbidities. 50A more recent report of the Hovon 143 study included 65 patients with NDMM who were characterized as intermediate-frail according to the IMWG frailty index 52 and received frontline treatment with Dara-Ixa-dex in the same dosing schedule, as previously. 51The ORR was 71%, whereas the median PFS was 18.2 months and the OS rate at 36 months was 83%.Although Hovon 143 was a phase 2 study, the 3-year OS outcomes are comparable to the well-established daratumumab-based upfront combinations for transplantineligible patients with NDMM including daratumumab with lenalidomide and dexamethasone (MAIA phase 3 study) 53,54 and daratumumab with bortezomib, melphalan and dexamethasone (ALCYONE phase 3 study). 55,56Other ixazomib-based combinations have been also applied in the frontline treatment with substantial efficacy and a tolerable toxicity profile both in phase 2 clinical trials and in the real-world with regards to convenience, accessibility or during the COVID-19 pandemic; however, no phase 3 clinical trials have supported the frontline use of ixazomib in patients with NDMM. 57,58egarding bone metabolism indices, the median changes from baseline for OC, bALP, CTX and TRACP-5b were statistically significant and became evident as early as at 3 months on treatment with Dara-Ixa-dex.Deregulated bone turnover, characterized by increased osteoclast activity and decreased osteoblast function is a hallmark for MM pathophysiology. 21A favorable effect on bone remodeling, which is mainly driven by the induction of bone formation, has been also previously reported in patients with RRMM who received monotherapy with daratumumab. 18In our study, all biomarkers indicative of bone formation (OC, bALP, PINP) 59 showed an increase, whereas OC emerged as a sensitive marker that showed a substantial increase from 3 months on treatment and thereafter.Osteoblast inhibitors, DKK1 60 and SOST, 61 showed a significant decrease after 1 year of treatment.Furthermore, CTX, which reflects bone destruction, showed a significant decrease only in patients who received long-term treatment.However, a transient increase in TRAC5b was noted at 6 months of treatment, which may indicate either an increased bone turnover or an early sign of disease progression before the documented disease progression according to the IMWG criteria.Dara-Ixa-dex did not seem to exert any effect on the levels of regulators of osteoclastic activity including RANKL and OPG. 62,63The interpretation of the findings on bone-related indices should be with caution, taking into consideration the small number of patients in each subgroup and the multiple comparisons.Furthermore, the small numbers precluded a comparative analysis of bone-related biomarkers according to the administration of bone-directed treatments that have a direct effect on bone metabolism. 64e Dara-Ixa-dex regimen was well tolerated and no new safety signals emerged.Less than half of the patients experienced serious (grade 3 or higher) adverse events.Hematologic toxicity and neuropathy were commonly reported, whereas infections were also frequent and some of them were severe.The toxicity profile was consistent with the safety outcomes reported with Dara-Ixa-dex in the relapsed/ refractory setting in the NCT03439293 study.Daratumumab has a multifaceted mechanism of action, it alters the immunological microenvironment and it may impair both humoral and cellular immunity. 7,65,66Patients with MM who receive treatment based on anti-CD38 monoclonal antibodies have a high risk of infections including severe and potentially lethal events, mainly in the respiratory tract. 67,68[76][77][78] In conclusion, second-line treatment with Dara-Ixa-dex in patients with RRMM pre-treated with a lenalidomide-based regimen resulted in rapid and sustained responses along with a favorable effect on bone metabolism with no new safety concerns.Although the efficacy may be inferior to other triplet combinations in the same disease setting, this regimen may be particularly suitable for patients intolerant to IMiDs and in cases of limited access to other novel drugs.Dara-Ixa-dex is a convenient treatment scheme that may reduce the frequency of hospital visits and the length of hospital stay, which in turn may reduce both patient burden and physician workload and may spare resources.

2 | METHODS 2 . 1 |
Study design and interventions DARIA was a prospective, open-label, multicenter, phase 2 study conducted in 5 sites in Greece (ClinicalTrials.govidentifier: NCT03746652).The recruitment began on December 18, 2018, and it was completed on September 2, 2020.Second-line treatment with Dara-Ixa-dex comprised an induction phase of nine 28-days cycles and a maintenance phase.During induction, patients received daratumumab at the approved schedule (weekly for the first 8 weeks, biweekly for 16 weeks and monthly thereafter), ixazomib at 4 mg per os on days 1, 8, and 15 of each cycle and dexamethasone per os at 40 mg weekly.Daratumumab was initially administered as an intravenous infusion at 16 mg/kg; however, all ongoing and new patients received subcutaneous daratumumab at 1800 mg beginning from November 2020 and thereafter following the positive results of the COLUMBA trial for non-inferiority. 10For participants older than 75 years or underweight (body mass index <18.5 kg/m 2 ), dexamethasone was administered at a dose of 20 mg weekly.During maintenance, dexamethasone was discontinued and daratumumab was administered every 4 weeks with ixazomib weekly (3 weeks on, 1 week off) until disease progression or unacceptable toxicity.The study was approved by the institutional review board, and it was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization for Good Clinical Practice.

F I G U R E 2
Kaplan-Meier curves of the PFS (A) and the OS (B) according to prior lenalidomide refractoriness.[Color figure can be viewed at wileyonlinelibrary.com]T A B L E 2 Summary of the changes in biomarker values over time.Patients with at least one biomarker assessment, L E 2 (Continued)Patients with at least one biomarker assessment,