Bendamustine is a type of DNA cross-linker that can lead to anti-helper function, alkylation, and DNA fragmentation. Bendamustine specifically affects the non-Hodgkin cell transplantation and DNA repair pathways. In SU-DHL-1 cells, bendamustine (50 μM) boosts p53 expression and promotes the NOXA and p21 (Cip1/Waf1) genes. Bendamustine (25 μM) disrupts mitotic checkpoints, leading to hyperplasia during mitosis [1]. Multiple myeloma (MM) cell lines such as RPMI-8226 and 8226-LR5 have lower cell viability when exposed to bendamustine; after 24 hours, the IC25 values of these lines are 101.8 μM and 585.5 μM, and after 48 hours, 51.7 and 374.3 μM, respectively. ..Bendamustine suppresses the spindle formation checkpoint and causes MM cell death triggered by caspase [2].

The DoHH-2, Granta 519, and RAMOS models showed 91%, 99%, and 95% inhibition of tumor cell proliferation in response to bendamustine (25 mg/kg, IV). Furthermore, rituximab improved the anticancer impact of bendamustine in the DoHH-2 and RAMOS models, but not in the Granta 519 model [3].

Subcutaneous Xenograft Model - Efficacy Study:** Female SCID or SCID-beige mice were subcutaneously inoculated with 1-5 x 10⁶ human non-Hodgkin's lymphoma cells (DoHH-2, Granta 519, RAMOS, SuDHL-4) mixed 1:1 with Matrigel in the right flank. Tumors were allowed to grow to approximately 250 mm³, at which point mice were size-matched into treatment groups (n=10 per group). Bendamustine was administered as a single intravenous (i.v.) dose at 25 mg·kg⁻¹ on day 0 (the day of size-matching). Navitoclax was administered orally, and rituximab was given i.v. Tumors were measured 2-3 times weekly with calipers. Tumor volume was calculated as (L x W²)/2. Mice were euthanized when tumors exceeded 2000 mm³ or if they showed signs of distress (e.g., >20% body weight loss) [1].
* **Systemic (Disseminated) Model:** C.B.-17 scid mice were inoculated intravenously (i.v.) via the tail vein with 2 x 10⁶ Granta 519 cells in 0.1 mL of medium on day 0. Treatment was initiated on day 14 post-inoculation after randomization. Bendamustine was administered as a single i.v. dose at 25 mg·kg⁻¹ on day 14. Navitoclax was given orally, and rituximab was given i.v. Mice were monitored daily for signs of morbidity (e.g., loss of ambulation, labored breathing) and euthanized upon reaching a morbidity endpoint [1].
* **Molecular Analysis in Tumors:** Granta 519 flank tumors were grown to approximately 500 mm³ and then treated with a single dose of bendamustine at 25 mg·kg⁻¹. Tumors (n=not specified per time point) were harvested at 4, 8, and 24 hours post-treatment. Half of each tumor was formalin-fixed for immunohistochemistry (IHC), and the other half was flash-frozen for Western blot analysis. IHC was performed on paraffin-embedded sections using an anti-cleaved caspase 3 antibody. Western blotting was performed on tumor homogenates using antibodies against p53, Noxa, and Mcl-1 [1].

Absorption, Distribution and Excretion
Following a single intravenous injection of bendamustine hydrochloride, peak plasma concentration (Cmax) typically occurs at the end of the infusion. The dose-proportionality of bendamustine has not been studied. Following intravenous infusion of [14C] bendamustine hydrochloride in cancer patients, the mean recovery of total radioactivity is approximately 76% of the dose. Approximately 50% of the dose is excreted in the urine, and approximately 25% in the feces. Urinary excretion has been shown to be a relatively minor route of elimination for bendamustine, with approximately 3.3% of the dose excreted unchanged in the urine. Less than 1% of the dose is recovered in the urine as M3 and M4, and less than 5% as HP2. The mean steady-state volume of distribution (Vss) of bendamustine is approximately 20–25 liters. The steady-state volume of distribution of total radioactivity is approximately 50 liters, indicating that neither bendamustine nor total radioactivity is widely distributed in tissues. Preclinical studies of radiolabeled bendamustine showed that approximately 90% of the administered drug was excreted primarily in feces. The clearance rate of bendamustine in the human body is approximately 700 mL/min. After a single intravenous injection of 120 mg/m² of bendamustine, the intermediate half-life of the parent compound is approximately 40 minutes after 1 hour. The mean apparent terminal elimination half-lives of M3 and M4 are approximately 3 hours and 30 minutes, respectively. Administration of bendamustine on days 1 and 2 of a 28-day cycle is expected to result in minimal or no accumulation of the drug in plasma. In vitro studies showed that bendamustine binds to human serum plasma proteins at a rate of 94-96%, regardless of concentration, within the range of 1-50 μg/mL. Data suggest that bendamustine is unlikely to replace or be replaced by drugs with high protein binding rates. The human serum plasma concentration ratio is 0.84-0.86 within the concentration range of 10-100 μg/mL, indicating that bendamustine is freely distributed in human erythrocytes. In humans, the average steady-state volume of distribution (Vss) is approximately 25 L.
Metabolism/Metabolites
In vitro data show that bendamustine is primarily metabolized via hydrolysis to monohydroxybendamustine (HP1) and dihydroxybendamustine (HP2) metabolites, which exhibit low cytotoxic activity. Two minor active metabolites, M3 and M4, are mainly generated via CYP1A2. However, the plasma concentrations of these metabolites are only 1/10 and 1/100 of the parent compound, respectively, indicating that their cytotoxic activity is primarily attributable to bendamustine. A human mass balance study confirmed that bendamustine is primarily metabolized via hydrolysis, oxidation, and conjugation pathways.
…Recently, it has been reported that bendamustine's thiouric acid metabolic pathway metabolites, namely cysteine S-conjugates, have been detected in human bile, and these metabolites are expected to undergo further metabolism. This study describes the identification and quantification of consecutive bendamustine metabolites in human bile using standards, as well as the synthesis and structural confirmation of these compounds. Mass spectrometry and high-performance liquid chromatography (HPLC) retention data (fluorescence detection) of the synthesized standards were consistent with data on metabolites found in human bile after cancer patients took bendamustine hydrochloride. Analysis of the purified synthetic standards showed a purity of at least 95%. Structural confirmation was achieved by one-dimensional and two-dimensional proton NMR spectroscopy, carbon-13 NMR spectroscopy, and mass spectrometry. A total of 16 bendamustine-related compounds were detected in patient bile, of which 11 were recovered as conjugates. The structures of 8 conjugates were confirmed as novel thiouric acid and sulfoxide. The bile excretion of sulfoxide was twice that of the thiouric acid precursor. Glutathione S-conjugates of bendamustine were not detected in bile samples, indicating rapid enzymatic degradation in the human body. The absence of glutathione (GSH) conjugates and the presence of diastereomer sulfoxides highlight the species-specific differences in GSH binding of bendamustine between humans and rats. Within 24 hours post-administration, the average total amount of conjugates recovered in bile was 5.2% of the administered dose. In vitro data indicate that bendamustine is primarily metabolized by hydrolysis to metabolites with lower cytotoxic activity. In vitro studies showed that the two minor active metabolites, M3 and M4, are mainly generated via CYP1A2. However, the plasma concentrations of these metabolites were only 1/10 and 1/100 of the parent compound, respectively, suggesting that their cytotoxic activity is primarily attributable to bendamustine. In vitro studies using human liver microsomes showed that bendamustine does not inhibit CYP1A2, 2C9/10, 2D6, 2E1, or 3A4/5. Bendamustine does not induce the metabolism of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2E1, or CYP3A4/5 enzymes in primary cultures of human hepatocytes.

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Biological Half-Life
40 minutes
One hour after a single intravenous injection of 120 mg/m² bendamustine, the intermediate half-life of the parent compound is approximately 40 minutes.

Hepatotoxicity
Up to 20% of patients receiving bendamustine treatment experience a mild, transient increase in serum transaminase levels, but less than 3% experience an increase exceeding 5 times the upper limit of normal. These abnormalities are usually transient, asymptomatic, and rarely require dose adjustment. Clinically significant liver injury caused by bendamustine is limited to a small number of mild hepatitis cases characterized by hypersensitivity reactions, including eosinophilia, rash, or other systemic symptoms. Autoantibody formation is uncommon. The course is usually self-limiting, but may require glucocorticoid therapy to control symptoms and promote timely recovery. Bendamustine treatment has also been associated with hepatitis B virus reactivation in patients with anti-HBc (with or without HBsAg) in their serum. In some cases, patients were concurrently receiving glucocorticoids or rituximab therapy but had not previously experienced reactivation with these treatments. Hepatitis B virus reactivation typically occurs after 2 to 6 cycles of bendamustine chemotherapy, manifesting as symptomatic HBsAg positivity and elevated HBV DNA levels. Reactivation is usually self-limiting, with the patient subsequently achieving HBsAg seroconversion. However, in one case, the condition was severe, ultimately leading to death from acute liver failure.
Probability Score: C (Possibly the cause of clinically significant liver damage, partly due to hepatitis B virus reactivation).

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Use during Pregnancy and Lactation
◉ Overview of Use During Lactation
There is currently no information regarding the use of bendamustine during lactation. Most sources consider breastfeeding contraindicated during maternal treatment with anti-tumor drugs, especially alkylating agents such as bendamustine. Based on the half-life of the drug and its metabolites, the drug should be cleared from breast milk within 24 to 48 hours after the last dose. The manufacturer recommends discontinuing breastfeeding during bendamustine treatment and for at least one week after the last dose.
◉ Effects on breastfed infants
As of the revision date, no relevant published information was found.
◉ Effects on lactation and breast milk
Some evidence suggests that carmustine, a drug closely related to carmustine, can increase serum prolactin levels.

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Protein binding
In vitro experiments show that bendamustine binds to human serum plasma proteins at a rate of 94-96%, suggesting that bendamustine is unlikely to replace or be replaced by drugs with high protein binding rates.

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Non-human toxicity values
Oral LD50 in rats: 200-300 mg/kg /bendamustine hydrochloride/ [Merck Index, 14th Edition (2006)]
Intravenous LD50 in rats: 40 mg/kg /bendamustine hydrochloride/ [Merck Index, 14th Edition (2006)]
Oral LD50 in mice: 400-500 mg/kg /bendamustine hydrochloride/ [Merck Index, 14th Edition (2006)]
Intravenous LD50 in mice: 80 mg/kg /bendamustine hydrochloride/ [Merck Index, 14th Edition (2006)]

[1]. Bendamustine (Treanda) displays a distinct pattern of cytotoxicity and unique mechanistic features compared with other alkylating agents. Clin Cancer Res. 2008 Jan 1;14(1):309-17.

[2]. Bendamustine overcomes resistance to melphalan in myeloma cell lines by inducing cell death through mitotic catastrophe. Cell Signal. 2013 May;25(5):1108-17.

[3]. Navitoclax (ABT-263) and bendamustine ± rituximab induce enhanced killing of non-Hodgkin's lymphoma tumours in vivo. Br J Pharmacol. 2012 Oct;167(4):881-91.

Therapeutic Uses

Anti-tumor drug/Bendamustine hydrochloride/[Merck Index, 14th edition (2006)]
Bendamustine hydrochloride is used to treat chronic lymphocytic leukemia (CLL) and is designated as an orphan drug by the U.S. Food and Drug Administration (FDA) for the treatment of this disease. /U.S. product label includes/
Bendamustine monotherapy is effective in rituximab-refractory indolent non-Hodgkin lymphoma, especially in patients who have not transformed or have sensitive disease characteristics. Therefore, bendamustine can be considered a reasonable option for rituximab-refractory indolent non-Hodgkin lymphoma; bendamustine can also be used as an alternative for patients who are not suitable for radioimmunotherapy due to patient selection (e.g., clinical contraindications) or accessibility issues. /U.S. product label includes/
Treanda for injection is an alkylating agent indicated for the treatment of patients with chronic lymphocytic leukemia (CLL). Its efficacy relative to first-line therapies other than chlorambucil has not been established. Indolent B-cell non-Hodgkin lymphoma (NHL) that has progressed during or within six months of treatment with rituximab or a rituximab-containing regimen. /US product label contains/
For more complete data on the therapeutic uses of bendamustine (of 8), please visit the HSDB record page.
Drug Warnings

Infections, including pneumonia and sepsis, have been reported in patients treated with bendamustine and can lead to hospitalization, septic shock, and death. Patients with myelosuppression are more susceptible to infection and should be advised to contact their clinician immediately if they develop signs or symptoms of infection.
In a phase 3 study of patients with chronic lymphocytic leukemia, 24% of patients treated with bendamustine experienced grade 3 or 4 neutropenia, and 3% experienced febrile neutropenia; 20% and less than 1% of patients, respectively, received red blood cell or platelet transfusions. For patients with bendamustine-related myelosuppression, white blood cell, platelet, hemoglobin, and neutrophil levels should be closely monitored. In a phase 3 study of bendamustine in the treatment of chronic lymphocytic leukemia, hemoglobin concentration, white blood cell count, and differential count were monitored weekly, and platelet count was monitored at each treatment cycle. Data from this study indicated that blood cell counts may reach their lowest point in the third week of treatment; if they do not return to recommended values by day 28, dosing may need to be delayed. Before starting the next treatment cycle, the absolute neutrophil count (ANC) should be at least 1000/mm³, and the platelet count should be at least 75,000/mm³. Tumor lysis syndrome has been reported in patients receiving bendamustine in both clinical trials and post-marketing surveillance. This syndrome typically occurs during the first cycle of bendamustine treatment; without appropriate intervention, it can lead to acute renal failure and death. For patients at high risk of tumor lysis syndrome, appropriate measures should be taken (e.g., adequate fluid resuscitation; close monitoring of blood biochemistry, especially potassium and uric acid levels; administration of allopurinol for the first 1-2 weeks of bendamustine treatment). Common infusion reactions in patients receiving bendamustine include fever, chills, itching, and rash. Severe anaphylactic and anaphylactoid reactions are rare, mainly occurring in the second and subsequent treatment cycles. Patients' clinical status should be closely monitored, and bendamustine should be discontinued immediately if a severe reaction occurs. After the first treatment cycle, patients should be asked about any symptoms suggestive of an infusion reaction. For patients experiencing Grade 1 or 2 infusion reactions, pre-treatment (e.g., antihistamines, antipyretics, and corticosteroids) should be considered for subsequent treatment cycles. For patients experiencing Grade 3 or 4 infusion reactions, discontinuation of bendamustine should be considered. In a phase 3 study of bendamustine in chronic lymphocytic leukemia, patients experiencing Grade 3 or more severe anaphylactic reactions typically did not receive further treatment with the drug.
For more complete data on bendamustine warnings (15 in total), please visit the HSDB records page.

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Pharmacodynamics
No mean change in QTc interval exceeding 20 milliseconds was detected within 1 hour after infusion.

C16H21N3O2CL2

358.26284

357.101

16506-27-7

Bendamustine hydrochloride;3543-75-7;Bendamustine-d4;Bendamustine-d8;1134803-33-0

65628

White to off-white solid powder

1.3±0.1 g/cm3

585.2±50.0 °C at 760 mmHg

307.7±30.1 °C

0.0±1.7 mmHg at 25°C

1.599

2.9

1

4

9

23

380

0

CN1C2=C(C=C(C=C2)N(CCCl)CCCl)N=C1CCCC(=O)O

YTKUWDBFDASYHO-UHFFFAOYSA-N

InChI=1S/C16H21Cl2N3O2/c1-20-14-6-5-12(21(9-7-17)10-8-18)11-13(14)19-15(20)3-2-4-16(22)23/h5-6,11H,2-4,7-10H2,1H3,(H,22,23)

4-[5-[bis(2-chloroethyl)amino]-1-methylbenzimidazol-2-yl]butanoic acid

Bendamustine free base; SDX 105; SDX-105; SDX105; Bendamustina; DD6304600; Bendamustinum; Ribomustin. Brand name: Treanda;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~279.13 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.98 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (6.98 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (6.98 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)