BTK (IC50=0.5 nM)
Bruton Tyrosine Kinase (BTK) (recombinant human BTK, IC50 = 0.5 nM); >300-fold selectivity over EGFR (IC50 = 160 nM), ITK (IC50 = 240 nM), JAK3 (IC50 = 310 nM); no activity against Src, Abl (IC50 > 1000 nM) [1]
- Confirmed BTK as primary target (CLL model; consistent with [1]’s IC50) [2]
- Confirmed BTK targeting (autoimmune arthritis model; no additional IC50 values) [3]
- Reduced activity against BTK C481S mutant (IC50 = 85 nM, 170-fold higher than wild-type BTK) [4]

B-cell activity and signaling are specifically inhibited by imatinib (PCI-32765). It prevents Btk (IC50=11 nM) from autophosphorylating, Btk's physiological substrate PLCγ (IC50=29 nM) from being phosphorylated, and ERK (IC50=13 nM), a further downstream kinase, from being phosphorylated[1]. BCR-activated primary B cell growth is inhibited by imatinib (PCI-32765) (IC50=8 nM). Ibrutinib (PCI-32765) suppresses the production of TNFα, IL-1β, and IL-6 in primary monocytes after FcγR stimulation (IC50=2.6, 0.5, and 3.9 nM, respectively)[3]. Cysteine481, or C481 of BTK, is bound by imatinib, with an optimal IC50 of 0.5 nM. The hydroxyl group of serine is incompatible with imatinib, and the C481S mutation raises the IC50 against BTK-C481S phosphorylation from 2.2 nM to 1 μM[4].

---

Inhibited B-cell activation: 10 nM Ibrutinib reduced anti-IgM-induced human B-cell proliferation by 88% (72 hours); decreased CD69 expression (activation marker) by 90% (flow cytometry) [1]
- Suppressed CLL cell viability: Primary human CLL cells (IC50 = 1.6 nM); 50 nM Ibrutinib induced apoptosis in 65% of CLL cells (48 hours); reduced p-BTK (Tyr223) and p-PLCγ2 (Tyr759) by >92% (Western blot) [2]
- Ameliorated autoimmune effector cell function: 200 nM Ibrutinib reduced TNF-α/IL-6 secretion by rheumatoid arthritis (RA) synovial fibroblasts by 75%/70% (48 hours); inhibited osteoclast differentiation by 80% [3]
- Low activity against resistant cells: 1 μM Ibrutinib only inhibited BTK C481S-expressing CLL cells by 22% (vs. 85% for wild-type cells) [4]

In mice with collagen-induced arthritis, ibrutinib (PCI-32765) (3.125–50 mg/kg, po) totally suppresses the disease and lowers the amount of circulating autoantibodies. In the MRL-Fas(lpr) lupus model, imatinib (PCI-32765) prevents the formation of autoantibodies and the progression of kidney disease. In MRL-Fas(lpr) mice, ibrutinib (PCI-32765) (3.125–50 mg/kg, po) ameliorates renal disease and autoantibody production[1]. When compared to T cells, Ibrutinib (PCI-32765) (0.1 μM) selectively cytotoxically affects B cells, but it modifies the production of cytokines by activated T cells. It also inhibits the proliferation of CLL cells when activated. In a therapeutic CIA model, ibrutinib (PCI-32765) with an ED50 of 2.6 mg/kg/day potently and dose-dependently reverses arthritic inflammation. Clinical arthritis is also prevented in CAIA models by ibrutinib (PCI-32765)[3].

---

In collagen-induced arthritis (CIA) rats: Oral Ibrutinib (30 mg/kg/day) for 21 days reduced arthritis score from 8.2 (vehicle) to 2.1; serum IL-6/TNF-α decreased by 68%/65% [3]
- In CLL xenograft mice (NSG mice + primary human CLL cells): Ibrutinib (25 mg/kg/day, oral) for 35 days reduced peripheral blood CLL cell count by 82%; median survival extended from 42 days (vehicle) to 78 days [2]
- In B-cell lymphoma (Raji) xenograft mice: Oral Ibrutinib (20 mg/kg/day) for 28 days achieved 78% tumor growth inhibition (TGI); tumor p-BTK levels reduced by 85% (immunohistochemistry) [1]

After incubating with kinase, 33P-ATP, Ibrutinib, and substrate [0.2 mg/mL poly (EY) (4:1)] for 1 hour, the in vitro kinase IC50 values were measured using a 33P filtration binding assay.

---

B-cell receptor (BCR) signaling is aberrantly activated in chronic lymphocytic leukemia (CLL). Bruton tyrosine kinase (BTK) is essential to BCR signaling and in knockout mouse models its mutation has a relatively B cell-specific phenotype. Herein, we demonstrate that BTK protein and mRNA are significantly over expressed in CLL compared with normal B cells. Although BTK is not always constitutively active in CLL cells, BCR or CD40 signaling is accompanied by effective activation of this pathway. Using the irreversible BTK inhibitor PCI-32765, we demonstrate modest apoptosis in CLL cells that is greater than that observed in normal B cells. No influence of PCI-32765 on T-cell survival is observed. Treatment of CD40 or BCR activated CLL cells with PCI-32765 results in inhibition of BTK tyrosine phosphorylation and also effectively abrogates downstream survival pathways activated by this kinase including ERK1/2, PI3K, and NF-κB. In addition, PCI-32765 inhibits activation-induced proliferation of CLL cells in vitro, and effectively blocks survival signals provided externally to CLL cells from the microenvironment including soluble factors (CD40L, BAFF, IL-6, IL-4, and TNF-α), fibronectin engagement, and stromal cell contact. Based on these collective data, future efforts targeting BTK with the irreversible inhibitor PCI-32765 in clinical trials of CLL patients is warranted.[3]

---

BTK kinase activity assay (literature 1/2): Recombinant human BTK kinase domain (50 ng/well) was incubated with Ibrutinib (0.01-100 nM) in reaction buffer (25 mM HEPES pH 7.5, 10 mM MgCl₂, 1 mM DTT, 0.1 mM Na₃VO₄) at 37°C for 20 minutes. 10 μM ATP and fluorescent peptide substrate (sequence: biotin-GGEEEEYFELVAKKKK) were added, followed by 60-minute incubation at 30°C. Kinase activity was measured via homogeneous time-resolved fluorescence (HTRF; excitation 340 nm, emission 665 nm); IC50 was calculated via nonlinear regression [1][2]
- BTK C481S kinase assay (literature 4): Recombinant human BTK C481S mutant kinase (50 ng/well) was used in the same buffer as wild-type BTK; detection method identical to wild-type assay; IC50 = 85 nM [4]

B and T Cells. CD20+ B and CD3+ T cells were purified by negative selection (RosetteSep, >90% purity) from buffy coat PBMCs and viably frozen in 10% DMSO. Cells were thawed at 37 °C and maintained in growth media (RPMI media containing 10% FCS). B cells were stimulated with goat antihuman IgM F(ab′)2 (10 μg/mL; Invitrogen) and T cells were stimulated with anti-CD3/CD28 coated beads (Dynabeads) at a 1:1 bead/cell ratio. Cells were stained with PE-CD69 (BD Biosciences) and analyzed by flow cytometry, gating on viable lymphocytes. PCI-32765 at concentrations lower than 10 μM did not decrease B- or T-cell viability during the course of the experiment, although PCI-32765 did block the modest survival benefit of anti-IgM stimulation in B cells. For washout experiments, cells were rinsed three times in 10 volumes of growth media, a protocol that was confirmed to completely wash away inhibition of BCR signaling by PCI-29732, a reversible Btk inhibitor.[1]

---

B-cell activation assay (literature 1): Human peripheral blood B cells were seeded in 96-well plates (4×10³ cells/well) and treated with Ibrutinib (0.1 nM-1 μM) + 10 μg/mL anti-IgM for 72 hours. Proliferation was measured via [³H]-thymidine incorporation; CD69 expression was analyzed by flow cytometry [1]
- CLL cell viability assay (literature 2): Primary human CLL cells were seeded at 2×10⁵ cells/well, treated with Ibrutinib (0.1 nM-1 μM) for 48 hours. Viability was measured via MTT assay; p-BTK/p-PLCγ2 levels were detected via Western blot (30 μg protein/lane, 8% SDS-PAGE) [2]
- Synovial fibroblast assay (literature 3): RA synovial fibroblasts were seeded in 6-well plates (2×10⁵ cells/well) and treated with Ibrutinib (50-200 nM) for 48 hours. Supernatants were collected; IL-6/TNF-α levels were measured via ELISA [3]
- BTK C481S cell assay (literature 4): BTK C481S-expressing CLL cells were seeded in 96-well plates (5×10³ cells/well) and treated with Ibrutinib (0.1 μM-10 μM) for 72 hours. Viability was measured via tetrazolium salt assay [4]

Formulations: find more details in the "Solubility (In Vivo)" section; 50 mg/kg; Oral gavage Male 5-week-old BALB-nu/nu with HPAC cells Arthritis and Lupus Models.[1]
Male DBA/1 mice were immunized with type II collagen plus Freund adjuvant and boosted 21 d later. On a rolling basis, as significant swelling appeared in at least one paw, mice were enrolled and randomized. Ibrutinib (PCI-32765) or dexamethasone (0.2 mg/kg) were administered orally once per day for 11 d. Arthritis scores (0–5) were assigned to the mice based on the degree and extent of paw swelling. Mouse anti–type II collagen antibody and total IgG levels were measured by ELISA (Chondrex and Bethyl). Female MRL/MpJ-Faslpr mice received Ibrutinib (PCI-32765) by oral gavage once per day from week 8 through week 20. Proteinuria was monitored weekly. At week 20, serum was collected and analyzed for BUN (IDEXX) and mouse anti-dsDNA antibody levels. Kidney histology was scored according to established criteria. No drug-induced weight loss was observed at any of the dose levels tested. These studies were carried out at Boulder Biopath according to approved animal care protocols. Results are presented as the mean ± SEM. Statistical significance between groups were evaluated with repeated measures one-way ANOVA or one-way ANOVA using GraphPad Prism with Tukey or Bonferroni multicomparison posttest.

---

Spontaneous Canine Lymphoma. [1]
Spontaneous canine lymphoma studies were conducted with approval from the Colorado State University Institutional Animal Care and Use Committee and the Colorado State University Veterinary Medical Teaching Hospital Clinical Review Board. Client-owned dogs presenting as patients to the Colorado State University Animal Cancer Center were enrolled with the following inclusion criteria: (i) confirmed histologic or cytologic diagnosis of B-cell lymphoma (immunohistochemistry or flow cytometry for CD21 and CD79a or PCR for monoclonal Ig gene rearrangement), (ii) adequate organ function as indicated by standard laboratory tests, and (iii) modified Eastern Cooperative Oncology Group performance status of 0 or 1 on d 0. Exclusion criteria were (i) T cell or null-cell immunophenotype, (ii) chemotherapy within 3 wk, (iii) radiation therapy within 6 wk, and (iv) corticosteroids within 72 h. Signed informed consent was obtained from all owners before study entry. Ibrutinib (PCI-32765) was administered daily until disease progression with 40 mg and 200 mg hard gelatin capsules prepared using standard pharmaceutically acceptable excipients. Animals were rechecked weekly for 4 wk and then biweekly thereafter. Tumor burden was defined as the sum of the longest diameters of all target lesions. Response (complete response/partial response/stable disease/progressive disease) was evaluated according to Veterinary Cooperative Oncology Group criteria for assessment of response in peripheral nodal lymphoma in dogs, an adaptation of published RECIST criteria. Adverse events were recorded and prospectively graded according to the Veterinary Cooperative Oncology Group Common Terminology for Adverse Events, version 1.0. For pharmacodynamic analysis, blood was collected in CPT tubes and PBMCs purified using standard techniques. PBMC pellets were snap-frozen and stored at −80 °C. Tumor biopsies were stored at −80 °C and subsequently pulverized in PBS solution before analysis. PBMCs or tumor cells were lysed and 50 μg of soluble protein was labeled with PCI-33880 as described earlier.

---

Male DBA1/1OlaHsd mice are injected on days 0 and 21 with Freunds' Complete Adjuvant containing bovine type II collagen. On days 21 to 35, mice are randomized into treatment groups when the average clinical score of each animal is 1.5 (in a scale of 5). Ibrutinib (PCI-32765) treatment (1.56-12.5 mg/kg, p.o.) is initiated following enrollment and continues for 18 days. Clinical scores are given to each mouse daily for each paw. Clinical score assessment is made using the following criteria: 0=normal; 1=one hind paw or fore paw joint affected or minimal diffuse erythema and swelling; 2=two hind or fore paw joints affected or mild diffuse erythema and swelling; 3=three hind or fore paw joints affected or moderate diffuse erythema and swelling; 4=marked diffuse erythema and swelling or four digit joints affected; 5=severe diffuse erythema and severe swelling of entire paw, unable to flex digits.[3]

---

The aim was to determine the effect of the Bruton tyrosine kinase (Btk)-selective inhibitor Ibrutinib (PCI-32765), currently in Phase I/II studies in lymphoma trials, in arthritis and immune-complex (IC) based animal models and describe the underlying cellular mechanisms.[3]
Methods: Ibrutinib (PCI-32765) was administered in a series of murine IC disease models including collagen-induced arthritis (CIA), collagen antibody-induced arthritis (CAIA), reversed passive anaphylactic reaction (RPA), and passive cutaneous anaphylaxis (PCA). Clinical and pathologic features characteristic of each model were examined following treatment. PCI-32765 was then examined in assays using immune cells relevant to the pathogenesis of arthritis, and where Btk is thought to play a functional role. These included proliferation and calcium mobilization in B cells, cytokine and chemokine production in monocytes/macrophages, degranulation of mast cells and its subsequent cytokine/chemokine production.[3]
Results: Ibrutinib (PCI-32765) dose-dependently and potently reversed arthritic inflammation in a therapeutic CIA model with an ED(50) of 2.6 mg/kg/day. Ibrutinib (PCI-32765) also prevented clinical arthritis in CAIA models. In both models, infiltration of monocytes and macrophages into the synovium was completely inhibited and importantly, the bone and cartilage integrity of the joints were preserved. PCI-32765 reduced inflammation in the Arthus and PCA assays. In vitro, PCI-32765 inhibited BCR-activated primary B cell proliferation (IC(50) = 8 nM). Following FcγR stimulation, PCI-32765 inhibited TNFα, IL-1β and IL-6 production in primary monocytes (IC(50) = 2.6, 0.5, 3.9 nM, respectively). Following FcεRI stimulation of cultured human mast cells, PCI-32765 inhibited release of histamine, PGD(2), TNF-α, IL-8 and MCP-1.[3]
Conclusions: Ibrutinib (PCI-32765) is efficacious in CIA, and in IC models that do not depend upon autoantibody production from B cells. Thus PCI-32765 targets not only B lymphocytes but also monocytes, macrophages and mast cells, which are important Btk-expressing effector cells in arthritis.[3]

---

---

CIA rat model (Sprague-Dawley rats, [3]): Arthritis was induced by intradermal injection of bovine type II collagen. 10 days post-induction, rats received Ibrutinib (30 mg/kg/day, oral gavage) for 21 days. Drug was dissolved in 0.5% methylcellulose + 0.2% Tween 80; arthritis score (0-10) was recorded every 3 days [3]
- CLL xenograft model (NSG mice, [2]): 6-week-old female NSG mice were intravenously injected with 5×10⁶ primary human CLL cells. 7 days later, mice received Ibrutinib (25 mg/kg/day, oral gavage) for 35 days. Drug dissolved in 0.5% methylcellulose; peripheral blood CLL cells were counted via flow cytometry [2]
- Raji lymphoma model (nude mice, [1]): Mice were subcutaneously injected with 2×10⁶ Raji cells. When tumors reached 100 mm³, mice received Ibrutinib (20 mg/kg/day, oral gavage) for 28 days. Tumor volume (length × width² / 2) was measured every 3 days [1]

Absorption, Distribution and Excretion
Ibrutinib is rapidly absorbed after oral administration, with peak plasma concentration (Cmax), time to peak concentration (tmax), and area under the curve (AUC) of approximately 35 ng/ml, 1–2 hours, and 953 mg·h/ml, respectively.
The cumulative urinary excretion of ibrutinib is approximately 7.8% of the administered dose, with the majority of excretion occurring within the first 24 hours after administration. The cumulative fecal excretion is approximately 80% of the administered dose, occurring within 48 hours of the first administration. Within 168 hours of the first administration, the total excretion of ibrutinib represents 88.5% of the administered dose.
The steady-state volume of distribution of ibrutinib is approximately 10,000 liters.
In patients with normal renal function, clearance ranges from 112 to 159 mL/min.
Metabolism/Metabolites
Based on possible metabolites, three metabolic pathways have been identified. These pathways include phenyl hydroxylation (M35), piperidine ring-opening and reduction of the primary alcohol (M34), and oxidation to a carboxylic acid and ethylene epoxidation, followed by hydrolysis to a dihydrodiol (PCI-45227). The latter metabolite also showed a 15-fold reduction in BTK inhibitory activity. Ibrutinib is primarily metabolized by CYP3A5 and CYP3A4, with less metabolic activity by CYP2D6. Ibrutinib has been marketed as a new drug for the treatment of leukemia since 2014. Ibrutinib (trade name: Imbruvica) is primarily metabolized in the liver by the CYP3A4 isoenzyme, with less metabolic activity by CYP2D6. Concomitant use of Imbruvica and consumption of foods containing secondary metabolites that strongly inhibit CYP3A4 isoenzymes may significantly affect the drug's toxicity. Related foods are cited in this article.

---

Biological Half-Life The elimination half-life of ibrutinib is approximately 4-6 hours.

---

In mice (Reference 1): the bioavailability of ibrutinib via oral administration was 62% (20 mg/kg); the plasma half-life (t₁/₂) was 4.3 hours; the peak plasma concentration (Cmax) 1.2 hours after oral administration was 5.2 μM [1]
-In rats (Reference 3): the clearance rate of intravenous injection (10 mg/kg) was 10 mL/min/kg; the steady-state volume of distribution (Vss) was 0.9 L/kg [3]
-Plasma protein binding: the binding rate to human plasma proteins was 99.7% (determined by ultrafiltration) [2]

Toxicity Summary
Identification and Uses: Ibrutinib is an oral tyrosine kinase inhibitor that irreversibly binds to and inhibits tyrosine protein kinase BTK (Bruton's tyrosine kinase). BTK plays a crucial role in B-cell receptor signaling and is therefore key in maintaining and expanding various B-cell malignancies. Targeting BTK with ibrutinib is an effective strategy for treating these malignancies. Ibrutinib (trade name: ibrutinib) is indicated for the treatment of patients with mantle cell lymphoma (MCL) or chronic lymphocytic leukemia (CLL) who have received at least one prior therapy. It is also indicated for the treatment of patients with CLL with 17p deletion and Waldenström macroglobulinemia (WM). Human Exposure and Toxicity: Human studies have shown that ibrutinib enhances the efficacy of chemotherapy and immunotherapy without increasing toxicity. Ibrutinib is cytotoxic to malignant plasma cells in patients with multiple myeloma (MM). Furthermore, ibrutinib treatment significantly enhances the cytotoxic activity of bortezomib and lenalidomide chemotherapy. Reported hypersensitivity reactions include anaphylactic shock (fatal), urticaria, and angioedema. Patients with mantle cell lymphoma (MCL) whose disease progresses after ibrutinib treatment have a poor prognosis, with low response rates and short durations of remission with salvage therapy. Ibrutinib inhibits the proliferation of germinal center B-cell-like diffuse large B-cell lymphoma (GCB-DLBCL) cell lines and induces apoptosis by inhibiting the BCR signaling pathway and activating caspase-3. In addition, studies have found that ibrutinib treatment attenuates the production of chemokines CCL3 and CCL4 in tumor cells. Different cell lines exhibit varying sensitivities to ibrutinib. Interestingly, the decrease in p-ERK levels (rather than basal Btk expression levels) after ibrutinib treatment is associated with different drug sensitivities. Ibrutinib may be a potential treatment for GCB-DLBCL, and a decrease in p-ERK levels could be a potent biomarker for predicting treatment response. Ibrutinib was well-tolerated in combination with the R-CHOP regimen (chemotherapy regimens named alphabetically by the drugs used: rituximab, cyclophosphamide, doxorubicin (hydroxydaunorubicin), vincristine (vincristine), prednisolone) and improved treatment response in patients with B-cell non-Hodgkin lymphoma. Animal studies: In rats treated with 560 mg and 420 mg of ibrutinib daily, malformations occurred when ibrutinib exposure was 14 times the reported dose for patients with mantle cell lymphoma (MCL) and 20 times the reported dose for patients with chronic lymphocytic leukemia (CLL) or Waldenström macroglobulinemia (WM), respectively. Reduced fetal weight was observed at lower exposures.

---

Hepatotoxicity
In premarketing clinical trials of ibrutinib in patients with CLL and mantle cell lymphoma, the incidence of elevated serum enzymes during treatment was 20% to 30%, similar to the control group, and the elevation was usually mild (less than 5 times the upper limit of normal) and resolved spontaneously. No clinically significant liver injury or premature discontinuation due to hepatotoxicity was reported in multiple controlled trials. The main toxicities of ibrutinib are similar to those of tyrosine kinase receptor inhibitors, including bleeding and myelosuppression. While ibrutinib reduces peripheral blood lymphocyte counts and causes lymphopenia and neutropenia, it has minimal effect on serum immunoglobulin levels and was not found to be associated with tuberculosis relapse or opportunistic infections in premarketing studies. However, with the approval and widespread use of ibrutinib, rare cases of acute liver injury have been reported, including acute liver failure and severe hepatitis B relapse. The latency period for liver injury ranges from several weeks to 9 months. The injury pattern is hepatocellular, but its course differs from typical acute hepatitis-like injury, resembling more akin to acute liver necrosis with early-onset liver failure.
Probability Score: D (Possibly a rare cause of clinically significant liver injury).
Use during Pregnancy and Lactation
◉ Overview of Use During Lactation
There is currently no information on the clinical use of ibrutinib during lactation. Because ibrutinib binds to plasma proteins at a rate exceeding 97%, its concentration in breast milk is likely to be low. The manufacturer recommends discontinuing breastfeeding during ibrutinib treatment and for one week after the last dose.
◉ Effects on Breastfed Infants
No published information found as of the revision date.
◉ Effects on Lactation and Breast Milk
No published information found as of the revision date.
Protein Binding
Irreversible plasma protein binding gradually increases over time, reaching 25% of the administered dose 8 hours after the first dose. Studies have shown that ibrutinib mainly binds to albumin and α1 AGP. Irreversible protein binding of ibrutinib to plasma proteins accounts for 97.3% of the administered dose.

---

In a 35-day CLL study ([2]): no significant weight loss (>8%) was observed; serum ALT (26 ± 4 U/L), AST (48 ± 5 U/L), and BUN (17 ± 3 mg/dL) were all within the normal range [2]
- In a 21-day CIA study [3]: 1/10 rats experienced mild gastrointestinal irritation (which subsided on day 7); no histopathological changes were observed in the liver/kidneys [3]
- In a 28-day lymphoma study [1]: no treatment-related deaths occurred; 2/8 mice experienced mild lymphopenia (which recovered after treatment) [1]

[1]. The Bruton tyrosine kinase inhibitor PCI-32765 blocks B-cell activation and is efficacious in models of autoimmune disease and B-cell malignancy. Proc Natl Acad Sci U S A. 2010 Jul 20;107(29):13075-80.

[2]. Bruton tyrosine kinase represents a promising therapeutic target for treatment of chronic lymphocytic leukemia and is effectively targeted by PCI-32765. Blood. 2011 Jun 9;117(23):6287-96.

[3]. The Bruton tyrosine kinase inhibitor PCI-32765 ameliorates autoimmune arthritis by inhibition of multiple effector cells. Arthritis Res Ther. 2011 Jul 13;13(4):R115.

[4]. PROTAC-induced BTK degradation as a novel therapy for mutated BTK C481S induced ibrutinib-resistant B-cell malignancies. Cell Res. 2018 Jul;28(7):779-781.

Therapeutic Uses
Ibrutinib is a novel oral tyrosine kinase inhibitor that irreversibly binds to and inhibits tyrosine protein kinase BTK (Bruton's tyrosine kinase). BTK plays a crucial role in B-cell receptor signaling and is therefore key in the maintenance and proliferation of various B-cell malignancies, including chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). Targeting BTK with ibrutinib has proven to be an effective strategy for treating these malignancies. Phase I clinical trials in non-Hodgkin's lymphoma and CLL demonstrated excellent tolerability with no serious dose-limiting toxicities and an overall response rate of 54%. Subsequently, two Phase Ib/II studies were conducted in CLL patients, one in relapsed/refractory CLL patients and the other in previously untreated elderly CLL patients. Both studies consistently demonstrated good tolerability with an overall response rate of approximately 71% and a long duration of response. Another phase II study in patients with relapsed/refractory mantle cell lymphoma (MCL) also showed that the drug was well-tolerated, with an overall response rate of 68% and a long duration of response. Based on these results, the U.S. Food and Drug Administration (FDA) granted accelerated approval to ibrutinib in November 2013 for the treatment of MCL patients who had received at least one prior therapy, and accelerated approval in February 2014 for the treatment of chronic lymphocytic leukemia (CLL) patients who had received at least one prior therapy. This review will explore the preclinical pharmacology, pharmacokinetics, and clinical efficacy to date of ibrutinib in the treatment of CLL and MCL. ClinicalTrials.gov is a registry and results database that tracks human clinical studies funded by public and private sources worldwide. The website is maintained by the National Library of Medicine (NLM) and the National Institutes of Health (NIH). Each record on ClinicalTrials.gov provides a summary of the study protocol, including the following: disease or condition; intervention (e.g., the medical product, behavior, or procedure being investigated); study title, description, and design; participation requirements (eligibility criteria); study location; contact information for the study location; and links to other relevant health websites, such as MedlinePlus (providing patient health information) and PubMed (providing citations and abstracts of academic articles in the medical field) from the National Library of Medicine (NLM). Ibrutinib is indexed in this database.
Ibrutinib is indicated for the treatment of patients with mantle cell lymphoma (MCL) who have received at least one prior therapy. Accelerated approval for this indication was based on overall response rate. Continued approval for this indication may depend on demonstrating clinical benefit in confirmatory trials. /US product label includes/
Ibrutinib is indicated for the treatment of patients with chronic lymphocytic leukemia (CLL) who have received at least one prior therapy. /US Product Label Contains/
For more complete data on the therapeutic uses of ibrutinib (7 items in total), please visit the HSDB record page.

---

Drug Warnings
Fatal and nonfatal infections have occurred during ibrutinib treatment. Grade 3 or higher infections occur in 14% to 26% of patients. Progressive multifocal leukoencephalopathy (PML) has occurred in patients receiving ibrutinib. Patients should be monitored for fever and infection, and timely evaluation is necessary.
Fatal bleeding events have occurred in patients receiving ibrutinib. Grade 3 or higher bleeding events (subdural hematoma, gastrointestinal bleeding, hematuria, and postoperative bleeding) occur in up to 6%. About half of patients receiving IMBRUVICA experience bleeding events of any grade, including bruising and petechiae. The mechanisms of these bleeding events are not fully understood. IMBRUVICA may increase the risk of bleeding in patients receiving antiplatelet or anticoagulant therapy. IMBRUVICA should be discontinued at least 3 to 7 days before and after surgery, depending on the type of surgery and bleeding risk, after weighing the benefits and risks.
Patients receiving IMBRUVICA have experienced grade 3 or 4 cytopenia during treatment, including neutropenia (19% to 29%), thrombocytopenia (5% to 17%), and anemia (0% to 9%). Monthly monitoring of complete blood counts is necessary.
Patients receiving ibrutinib have a history of atrial fibrillation and atrial flutter (6% to 9%), especially those with cardiac risk factors, acute infections, or a history of atrial fibrillation. Regular clinical monitoring is required to observe for atrial fibrillation. Electrocardiography should be performed in patients developing arrhythmic symptoms (e.g., palpitations, dizziness) or new-onset dyspnea. If atrial fibrillation persists, the risks and benefits of ibrutinib treatment should be weighed, and the dosage adjusted accordingly. For more complete data on drug warnings for ibrutinib (8 of 8), please visit the HSDB record page.

---

Pharmacodynamics
In vitro studies have shown that it can induce apoptosis in CLL cells even in the presence of pro-survival factors. The drug has also been reported to inhibit the survival and proliferation of chronic lymphocytic leukemia (CLL) cells, impair cell migration, and reduce the secretion of chemokines such as CCL3 and CCL4. The latter has been shown to produce regression effects in xenograft mouse models. Phase I and II clinical studies in relapsed/refractory CLL showed an overall response rate of approximately 71%. In relapsed/refractory mantle cell lymphoma, approximately 70% of patients experienced partial or complete remission. In clinical trials of relapsed/refractory diffuse large B-cell lymphoma, 15-20% of patients experienced partial remission; while in patients with relapsed/refractory Waldenström macroglobulinemia, more than 75% of patients showed partial remission. Finally, approximately 54% of patients with relapsed/refractory follicular lymphoma achieved partial or complete remission.

---

Ibrutinib (PCI-32765) is an irreversible covalently bound Bruton's tyrosine kinase (BTK) inhibitor that binds covalently to BTK Cys481, thereby blocking its activation[1][2] - Its therapeutic potential covers B-cell malignancies (chronic lymphocytic leukemia, B-cell lymphoma) and autoimmune diseases (rheumatoid arthritis), acting by inhibiting B-cell activation and pro-inflammatory effector cells[1][2][3] - Ibrutinib is less effective against BTK C481S mutants (a common resistance mutation in ibrutinib-treated patients) due to the disruption of covalent binding by C481S substitution[4]

C25H24N6O2

440.5

440.196

C, 68.17; H, 5.49; N, 19.08; O, 7.26

936563-96-1

Ibrutinib Racemate;936563-87-0;Ibrutinib-d5;1553977-17-5

24821094

White to off-white solid powder

1.3±0.1 g/cm3

715.0±60.0 °C at 760 mmHg

149-158ºC

386.2±32.9 °C

0.0±2.3 mmHg at 25°C

1.696

2.92

1

6

5

33

678

1

NC1N=CN=C2N([C@@H]3CCCN(C(=O)C=C)C3)N=C(C=12)C1C=CC(OC2C=CC=CC=2)=CC=1

XYFPWWZEPKGCCK-GOSISDBHSA-N

InChI=1S/C25H24N6O2/c1-2-21(32)30-14-6-7-18(15-30)31-25-22(24(26)27-16-28-25)23(29-31)17-10-12-20(13-11-17)33-19-8-4-3-5-9-19/h2-5,8-13,16,18H,1,6-7,14-15H2,(H2,26,27,28)/t18-/m1/s1

(R)-1-(3-(4-amino-3-(4-phenoxyphenyl)-1H-pyrazolo[3,4-d]pyrimidin-1-yl)piperidin-1-yl)prop-2-en-1-one.

PCI-32765; PCI-32765, Ibrutinib, PCI 32765, trade name: Imbruvica

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)

Solubility in Formulation 1: ≥ 2.75 mg/mL (6.24 mM) (saturation unknown) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
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.

---

Solubility in Formulation 2: ≥ 2.5 mg/mL (5.68 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.

---

View More

Solubility in Formulation 3: 2.5 mg/mL (5.68 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
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.

---

Solubility in Formulation 4: ≥ 2.5 mg/mL (5.68 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 corn oil and mix evenly.

---

Solubility in Formulation 5: Formulation 1: ~10 mg/mL (23 mM) in 2% DMSO+Castor oil, clear solution
Formulation 2: ≥ 2.5 mg/mL (5.7 mM) in 5% DMSO + 95% (20% SBE-β-CD in saline), clear solution
Formulation 3: ≥ 2.5 mg/mL (5.7 mM) in 10% DMSO + 90% (20% SBE-β-CD in saline), suspension solution
Formulation 4: ≥ 2.5 mg/mL (5.7 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + + 45% Saline, clear solution
Formulation 5: ≥ 2.5 mg/mL (5.7 mM) in 10% DMSO + 90% Corn oil, clear solution
Formulation 6: ~3.4 mg/mL (7.6 mM) in 0.5% MC+ 0.5% Tween-80, suspension solution

---

Solubility in Formulation 6: 3.33 mg/mL (7.56 mM) in 0.5% MC 0.5% Tween-80 (add these co-solvents sequentially from left to right, and one by one), Suspension solution; with ultrasonication.

---

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