EARLY Results of TOTAL Therapy 7 (TT7): High Response Rates of NEWLY Diagnosed High Risk Myeloma to Daratumumab

Background. The TT approach has significantly improved the outcome of multiple myeloma (MM) by combining new drugs with a regimen that comprises induction, tandem autologous stem cell transplantation (ASCT), consolidation and maintenance. However, a group of 15% of patients with high risk multiple myeloma (HRMM) have derived little benefit despite similar response rates to induction chemotherapy and ASCT when compared to low risk MM. The poor outcome of HRMM is explained by early relapse post ASCT resulting in a short progression free survival (PFS) with only 15-20% of patients surviving long-term. Daratumumab (Dara) is a human IgG1k anti-CD38 monoclonal antibody that has shown favorable results in early single-arm studies and more recently in phase III studies for relapsed/refractory and newly diagnosed MM. In TT7, we introduced Dara during all phases of therapy, including immune consolidation early post ASCT, to improve responses rate and PFS in HRMM.

Methods. Patients had newly diagnosed HRMM as defined by high risk cytogenetic abnormalities, presence of extramedullary disease, >3 focal lesions on CT-PET, elevated LDH due to MM, or ISS II/III with cytogenetic abnormality. Dara (16mg/kgx1) was added to induction with KTD-PACE (carfilzomib, thalidomide, dexamethasone; and four-day continuous infusions of cisplatin, doxorubicin, cyclophosphamide, etoposide). Conditioning for tandem autologous stem cell transplantation (ASCT) was with fractionated melphalan (50mg/m²x4) (fMEL) based on prior observations that patients with adverse cytogenetics fare better with fMEL rather than single high dose MEL200mg/m².In the inter tandem ASCT period immunological consolidation with Dara (16mg/kg) alone for 2 doses was followed by Dara (16mg/kg) on day 1 combined with K (36mg/m²) and D (20mg) weekly for 2 cycles. DaraKD was administered to avoid treatment free periods allowing for myeloma regrowth. The 2^nd ASCT was followed by further immunological consolidation with Dara (16mg/k) for 2 doses, and maintenance therapy for 3 yrs with 3-months block of alternating Dara-KD (dara 16mg/kg day 1; K 36mg/m² and dex 20mg weekly) and Dara-lenalidomide (R)D (dara 16mg/kg day 1; R 15mg day 1-21 q28 and D 20mg weekly).

Results. TT7 enrolled 43 patients thus far. The median follow-up was 11 months (range: 1-22). The median age was 61 yrs (range 44-73). Sixteen patients were ≥65 yrs (37.2%). A mean of 29.4x10⁶ CD34⁺ cells/kg (range: 4.6-86.4) were collected. 36 patients completed ASCT #1 (83.7%) and 18 (41.9%) ASCT #2, whilst 14 patients have proceeded to the maintenance phase. R-ISS II/III or metaphase cytogenetic abnormalities were present in 85.1 and 58.1% of patients, respectively. Elevated LDH or >3FL on CT-PET were noted in 30 and 41.8%. The 1-yr cumulative incidence estimates for reaching VGPR and PR were 87 and 83%, respectively. A CR or sCR was achieved in 68 and 46%. The 1-yr estimates of PFS and OS were 91.6 and 87.2%. 40 subjects are alive, whilst 5 progressed on study therapy and 3 subsequently died. 38 patients are progression free at the time of reporting. Dara was well-tolerated and no subjects discontinued therapy due to dara-related side effects. The CR and sCR rates compared favorably to the predecessor HRMM TT5 protocol where CR and sCR rates were 59 and 27%.

Conclusion. The early results of TT7 point to increased response rates of HRMM to a dara-based TT regimen with especially higher rates of CR and sCR. Longer follow-up is required to determine if these early results translate into superior PFS and OS.

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