How Daratumumab Is Used to Treat Multiple Myeloma

Daratumumab has reshaped how multiple myeloma is treated at nearly every stage of the disease. As the first monoclonal antibody to target the CD38 protein on myeloma cells, it earned approval based on striking trial results: when added to standard drug combinations, it roughly halved the risk of disease progression or death across multiple large trials, whether patients were newly diagnosed or had relapsed after prior therapy. That kind of consistent benefit across settings is unusual in oncology, and it explains why daratumumab has moved from a last-resort option for heavily treated patients to a cornerstone of front-line treatment in just a few years. The drug’s story, though, is more complex than a simple success narrative. It comes with real trade-offs in infection risk, logistical challenges in blood banking, and cost pressures that limit access for many patients worldwide.

How Daratumumab Kills Myeloma Cells

CD38 is a protein found at high levels on the surface of myeloma cells. Daratumumab locks onto CD38 and triggers several overlapping mechanisms to destroy those cells. The antibody flags myeloma cells for attack by natural killer cells, a process called antibody-dependent cell-mediated cytotoxicity. It also activates the complement system, a cascade of blood proteins that punch holes in the cell membrane. A third route involves macrophages, immune cells that essentially engulf and digest the tagged myeloma cells.¹ Daratumumab can also trigger a form of programmed cell death directly and interfere with CD38’s enzymatic activity.²

Beyond direct tumor killing, daratumumab has a second, less obvious benefit: it removes certain immune cells that protect the cancer. Myeloma tumors are surrounded by regulatory T cells, regulatory B cells, and myeloid-derived suppressor cells that dampen the body’s own anti-tumor immune response. Many of these suppressive cells also carry CD38 on their surface. When daratumumab eliminates them, the remaining T cells expand and diversify, essentially loosening the brakes on the immune system’s ability to attack myeloma.³ This immunomodulatory action likely contributes to the deep and durable responses seen in clinical trials.

Results in Newly Diagnosed Patients Who Cannot Have a Transplant

Many people diagnosed with myeloma are older or have other health conditions that make high-dose chemotherapy followed by a stem-cell transplant too risky. For these patients, the MAIA trial tested adding daratumumab to the widely used combination of lenalidomide and dexamethasone. At about two and a half years of follow-up, roughly 71% of patients receiving the daratumumab combination were alive without disease progression, compared with about 56% on lenalidomide and dexamethasone alone.⁴ With longer follow-up approaching five years, the median time before the disease worsened had still not been reached in the daratumumab group, while the control group’s median was about 34 months.⁵

Quality of life data from this same trial showed that improvements in pain, fatigue, and physical functioning were sustained over five years in patients receiving the daratumumab combination. By about three years of treatment, patients on daratumumab were roughly twice as likely to have experienced meaningful improvement in fatigue and physical functioning compared with those on the two-drug regimen alone.⁶ That finding matters because adding a drug to a cancer regimen often worsens side effects enough to erode any gains in disease control. Here, the added drug not only controlled the disease longer but also left patients feeling better during treatment.

Results in Transplant-Eligible Patients

For younger, fitter patients who can tolerate transplant, daratumumab has been tested as part of a four-drug induction regimen alongside bortezomib, lenalidomide, and dexamethasone. In the PERSEUS trial, adding daratumumab to this standard triplet produced four-year progression-free survival of about 84%, compared with roughly 68% for the triplet alone. The rate of complete response or better also jumped to about 88% in the four-drug group versus 70% in the three-drug group.⁷

A meta-analysis pooling data from multiple trials of daratumumab-based quadruplet regimens against triplet regimens in transplant-eligible patients found a consistent survival advantage. The risk of death was reduced by about 40%, and the risk of disease progression or death was cut roughly in half.⁸ The low variability across studies in that analysis suggests the benefit is reliable and not driven by one outlier trial.

Retreating Relapsed or Refractory Disease

Before daratumumab moved to the front line, it proved itself in patients whose disease had returned after at least one prior treatment. In the landmark POLLUX trial, adding daratumumab to lenalidomide and dexamethasone in relapsed or refractory patients produced a 12-month progression-free survival rate of about 83%, compared with 60% for the two-drug regimen alone. The overall response rate climbed from about 76% to 93%.⁹ With extended follow-up of nearly seven years, the median overall survival was about 68 months for daratumumab-treated patients versus roughly 52 months for the control group, a difference of more than a year and a half.¹⁰

In a parallel trial called CASTOR, daratumumab was paired with bortezomib and dexamethasone for relapsed patients. The median progression-free survival nearly doubled: about 17 months with the daratumumab combination versus roughly 7 months without it. Subgroup analyses showed these benefits held regardless of patient age.¹¹ Across both trials, patients in the daratumumab arms were more likely to achieve minimal residual disease (MRD) negativity, meaning no detectable cancer at extremely sensitive thresholds, and those who reached that depth of response had longer remissions.¹²

Maintenance After Transplant

Once a patient completes induction therapy and transplant, maintenance treatment aims to keep the disease suppressed for as long as possible. Lenalidomide alone has been the standard maintenance drug for years, but trials are now testing whether adding daratumumab extends that benefit. In the AURIGA study, the combination of daratumumab plus lenalidomide roughly tripled the rate at which patients converted to MRD negativity within the first year after transplant compared with lenalidomide alone: about 51% versus 19%. The estimated 30-month progression-free survival rate was about 83% for the combination versus 66% for lenalidomide alone.¹³

The CASSIOPEIA trial explored daratumumab monotherapy as maintenance after transplant. At an extended median follow-up, patients who received daratumumab maintenance had substantially longer progression-free survival than those on observation alone. The benefit was particularly pronounced for patients whose initial induction did not include daratumumab, suggesting that exposure to the drug at any point in the treatment journey can add value.¹⁴

The Subcutaneous Version and What It Changed

Intravenous daratumumab infusions are slow. The first dose takes a median of about seven hours because the rate must be carefully escalated to manage infusion reactions. About half of patients experience some kind of reaction during the first IV infusion, usually chills, cough, or nasal congestion. The development of a subcutaneous formulation co-formulated with an enzyme called hyaluronidase changed the logistics dramatically. The injection takes about three to five minutes, and infusion-related reactions drop to under 10%.¹⁵ Studies in Japanese patients confirmed similar tolerability and response rates with the subcutaneous version, and no infusion reactions at all were observed in one cohort.¹⁶

For patients who receive daratumumab indefinitely until their disease progresses, shaving hours off each visit is more than a convenience issue. It reduces time away from work or family, lowers the burden on infusion centers, and makes the treatment more sustainable over the months and years that maintenance therapy requires. Most clinics have now shifted to the subcutaneous version as the default.

Infection Risk and How to Manage It

The flip side of daratumumab’s immune effects is that it lowers the body’s defenses against infections. CD38 is found on natural killer cells and other immune cells, and their depletion leaves patients more vulnerable. A systematic review and meta-analysis of daratumumab-containing regimens found a meaningfully increased risk of infections, particularly pneumonia and respiratory infections.¹⁷ Antibody levels also fall. One study found that average immunoglobulin G levels dropped from about 568 mg/dL before daratumumab to about 371 mg/dL afterward, and the proportion of patients with clinically low antibody levels rose from roughly 64% to 88%.¹⁸

This makes proactive infection prevention essential. International guidelines recommend pneumococcal, influenza, and COVID-19 vaccination; antiviral prophylaxis for herpes zoster; monitoring of immunoglobulin levels; and intravenous immunoglobulin replacement for patients who develop severe or recurrent infections with low antibody levels.¹⁹ The same study tracking immunoglobulin levels found that the infection rate was roughly 2.4 times higher during periods when patients were not receiving immunoglobulin replacement, suggesting that timely supplementation makes a measurable difference.²⁰

Interference with Blood Typing and Lab Monitoring

Daratumumab creates a practical headache that every patient and blood bank technician should know about. Because CD38 is weakly expressed on red blood cells, daratumumab in the patient’s serum binds to reagent red cells used in compatibility testing, causing a false-positive reaction that looks like the patient has antibodies against virtually all blood types. This panreactive pattern can delay or complicate transfusions.²¹²² Blood banks now use workarounds, most commonly treating test cells with a reagent called dithiothreitol (DTT) that denatures CD38 and eliminates the interference. Patients are also advised to have their blood typed before starting daratumumab and to carry a card noting their treatment, so that in an emergency, the blood bank can take the appropriate steps without delay.

A separate lab issue involves how doctors monitor the disease itself. Myeloma is tracked by measuring abnormal protein (M-protein) in the blood. Daratumumab is itself an antibody, an IgG-kappa protein, and it can show up as a small spike on serum protein electrophoresis that mimics or obscures the myeloma’s own M-protein. This can lead to confusion about whether the disease is truly in remission or whether the “spike” on the test is just the drug itself.²³ Specialized assays have been developed to distinguish daratumumab from the tumor’s protein, and awareness of this interference has improved over the years, but it remains a source of occasional misinterpretation.

High-Risk Genetics and Their Limits

Not all myeloma behaves the same way. Certain chromosomal abnormalities, such as deletion of part of chromosome 17 or specific translocations, mark a disease that tends to relapse faster and be harder to control. A natural question is whether daratumumab overcomes these high-risk features. A meta-analysis looking specifically at this found that daratumumab does improve outcomes for patients with high-risk cytogenetics compared with the same regimens without it. However, it does not completely erase the disadvantage conferred by these mutations. Patients with high-risk changes still do worse on average than standard-risk patients on the same daratumumab regimen.²⁴ That gap has motivated ongoing research into additional strategies for this subgroup, including newer immunotherapies like bispecific antibodies and CAR-T cell therapy.

When Daratumumab Stops Working and the Question of Retreatment

Resistance to daratumumab develops over time in most patients. Several mechanisms contribute, including a reduction in CD38 expression on myeloma cells, which removes the target the drug needs to bind. Changes in the immune microenvironment and shifts in how well the complement and immune-cell pathways function also play roles.²⁵

An interesting clinical question is whether patients who become resistant to daratumumab can respond to it again after a break. Laboratory work suggests that sensitivity to daratumumab partially recovers after a washout period. In one study, myeloma cells from patients who had been off daratumumab for more than a year showed restored sensitivity in lab testing, while cells from patients off the drug for less than a year mostly did not.²⁶ Clinical retreatment data back this up. In a study of daratumumab-refractory patients retreated with daratumumab-based combinations after intervening therapy, about half responded, with a median progression-free survival of roughly eight months and a median overall survival of nearly three years.²⁷ This is not a dramatic response by front-line standards, but for patients running low on treatment options, recycling a previously effective drug class has genuine value.

The Cost Problem

Daratumumab is expensive, and it is typically given continuously until the disease progresses, which can mean years of treatment. A cost-effectiveness analysis for transplant-ineligible patients estimated lifetime treatment costs of about $1.4 million when daratumumab was used in the first-line setting versus about $1.1 million when it was held in reserve for later use. The incremental cost per quality-adjusted life year gained exceeded $600,000, far above standard willingness-to-pay thresholds in the United States. The authors calculated that the drug’s price would need to drop by roughly two-thirds for front-line use to be considered cost-effective.²⁸ A separate modeling study reached a similar conclusion, recommending an upfront price reduction as the clearest path to making first-line use economically viable.²⁹

This creates a tension that oncologists navigate daily. The clinical evidence strongly favors adding daratumumab as early as possible, but in health systems with constrained budgets, that evidence collides with affordability. In many countries, access to daratumumab remains limited or restricted to later lines of therapy, even though the survival data argue for earlier use. The subcutaneous formulation helps somewhat by reducing infusion-center chair time and staffing costs, but the drug itself remains the dominant expense.

Where Daratumumab Fits Among Newer Immunotherapies

The myeloma treatment landscape is evolving rapidly. Bispecific antibodies and CAR-T cell therapies have emerged as options for patients who have exhausted traditional treatments, including daratumumab. Bispecific antibodies work by physically bridging a T cell to a myeloma cell, triggering direct killing. Some of these newer agents target different proteins on myeloma cells, such as BCMA or GPRC5D, meaning they can work even after daratumumab resistance develops. Clinical trials are now exploring whether bispecific antibodies and anti-CD38 antibodies can be combined or sequenced to extend the period of disease control.³⁰ For most patients today, daratumumab remains the first immunotherapy they encounter, and the question of what comes after it when it stops working is one of the most active areas of myeloma research. Rather than replacing daratumumab, these newer tools are filling the gap that opens once CD38-directed therapy is no longer effective.