High-dose Methotrexate Combined with Thiotepa and Zanubrutinib in the Treatment of Newly Diagnosed PCNSL (MTZ)

PCNSL is a rare extranodal aggressive lymphoma accounting for 4%- 6% of all extranodal lymphomas and 3%- 4% of brain tumors, with an overall low incidence rate. However, with the extension of life expectancy, the incidence of PCNSL has increased by 2-3 times in Western Europe and the United States over the past 20 years.

Conventional dose methotrexate (MTX) does not effectively cross the blood-brain barrier, and the treatment for newly diagnosed PCNSL is still based on high-dose methotrexate (HD-MTX) combined chemotherapy. In the early stages PCNSL, Batchelor et al. used an MTX dose of 8.0g/m², which could reach effective therapeutic concentrations in the cerebrospinal fluid (CSF). However, HD-MTX has significant nephrotoxicity, especially for elderly patients and those with renal insufficiency. In 2005, Khan et al. found that reducing the dose of MTX to 3.5g/m² could significantly reduce kidney toxicity. Although single-agent HD-MTX has some efficacy in treating PCNSL, the remission rate is still relatively low. High doses of cytarabine, dacarbazine, and thiotepa have a higher blood-brain barrier penetration rate, and these drugs combined with HD-MTX for treating PCNSL can further improve upon HD-MTX alone. The overall response rate (ORR) is approximately 60%-70%, the complete response (CR) rate is about 40%-50%, and the 5-year survival rate is around 30%. Neither the short-term efficacy nor the long-term survival is satisfactory.

Basic research has found that excessive activation of the BCR signaling pathway in PCNSL tumor tissue, and BTK inhibitors such as ibrutinib can effectively inhibit the BCR pathway to achieve therapeutic goals. A study used single agent ibrutinib to treat relapsed/refractory PCNSL, with an overall response rate (ORR) of 50%. Grommes et al. reported that ibrutinib combined with high-dose methotrexate (HD-MTX) with or without rituximab showed specific efficacy in treating relapsed/refractory PCNSL, with an ORR of 89% and a complete response (CR) rate of 67%. The efficacy was significantly higher than that of single-agent ibrutinib in treating relapsed/refractory PCNSL.

Based on these studies, we hypothesize that first-line treatment with BTK inhibitors combined with HD-MTX-based chemotherapy may further improve the efficacy of newly diagnosed PCNSL and prolong the duration of remission.However, as a first-generation BTK inhibitor, ibrutinib has a relatively high off-target effect, leading to increased drug resistance and adverse reaction rates. Zanubrutinib, as a new generation of BTK inhibitors, has shown more potent antitumor activity and lower adverse reactions than ibrutinib in head-to-head clinical studies. Previously, we conducted a phase II clinical study of ibrutinib combined with methotrexate and temozolomide in PCNSL, which showed that ibrutinib significantly improved patients' overall response rate and complete response rate. However, the duration of remission was relatively short. Therefore, this study uses the new generation of zanubrutinib and thiotepa, which have intense penetration into the central nervous system, aiming to improve patients' remission duration further.

At the same time, based on previous studies and clinical experience, elderly and patients with renal insufficiency have poor tolerance to methotrexate, often experiencing delayed MTX clearance and renal damage. The first four courses of this study removed methotrexate and only used the less toxic zanubrutiniba and thiotepa, providing a reference for future methotrexate-free treatment options.

Inclusion criteria

• Men and woman who are 18 to 70 years of age
• Histologically documented PCNSL
• ECOG performance status ≤ 2
• Life expectancy of > 3 months
• Imaging show at least one measurable lesion in the central nervous system.
• Adequate bone marrow and organ function shown by:
• Absolute neutrophil count (ANC) ≥ 1.5 x 10^9/L
• Platelets ≥ 75 x 10^9/L and no platelet transfusion within the past 14 days
• Hemoglobin (Hgb) ≥ 8 g/dL and no red blood cell (RBC) transfusion within the past 14 days
• International Normalized Ratio (INR) ≤ 1.5 and PTT (aPTT) ≤ 1.5 times the upper limit of normal
• Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3×ULN
• Serum bilirubin ≤ 1.5×ULN
• Serum creatinine ≤ 2×ULN
• Lipase ≤ 1.5 x LUN
• Women of childbearing potential (WOCBP) and men must agree to use effective contraception when sexually active. Women of childbearing potential must have a negative serum pregnancy test within 7 days prior to the first dose of medication; women who are pregnant or breastfeeding are not eligible to participate in this study. Women of childbearing potential: from the time of signing the Informed Consent Form (ICF) until 30 days after the study ends, sexually active men: from the time of signing the ICF until 90 days after the study ends, must use contraceptive measures.
• Must be able to tolerate MRI/CT scans
• Must be able to tolerate lumbar puncture and/or Ommaya tap

Exclusion criteria

• Diagnosed with a malignant tumor other than PCNSL or has received treatment, except for the following cases:

• Received curative treatment and has no known active disease at least 3 years or more before screening for enrollment.
• Fully treated non-melanoma skin cancer or malignant lentigo, with no evidence of disease.
• Fully treated carcinoma in situ, with no evidence of disease currently.
• Clinically significant cardiovascular disease such as uncontrolled or symptomatic arrhythmias, congestive heart failure (New York Heart Association > Class 2), unstable angina, or myocardial infarction within 6 months of screening, or any Class 3 or 4 cardiac disease as defined by the New York Heart Association Functional Classification
• Uncontrolled hypertension despite optimal medical management (per investigators assessment)
• Patient has poorly controlled diabetes (per investigators assessment)
• Patient is known to have an uncontrolled active systemic infection (>CTCAE grade 2) and recent infection requiring intravenous anti-infective treatment that was completed ≤14 days before the first dose of study drug
• Cerebrovascular accident, deep vein thrombosis or pulmonary embolism within 3 months before the start of study treatment
• Non-healing wound, ulcer or bone fracture in a short time
• Known bleeding diathesis or hemophilia
• Known history of infection with human immunodeficiency virus (HIV) or active stage of infection with hepatitis C virus (HCV) or hepatitis B virus (HBV) . Active HBV infection must be confirmed by a positive test for HBV surface antigen or a positive test for hepatitis B core antibody with a positive determination of HBV DNA by polymerase chain reaction (PCR). For Hepatitis C virus (HCV), confirmation must be made by a positive test for HCV antibodies, unless the subject has been treated and has shown a sustained virological response. Note: Subjects with positive HCV antibodies who have been treated and have shown a sustained virological response (negative virus detection for at least 6 months after completing treatment) will not be excluded.
• Patient underwent major systemic surgery ≤ 2 weeks prior to starting the trial treatment or who has not recovered from the side effects of such surgery
• Unable to swallow capsules or disease significantly affecting gastrointestinal function
• Life-threatening illness, medical conditions, or organ dysfunctions that may endanger the safety of the subject or put the study outcomes at risk.
• Lactating or pregnant
• Requires anticoagulation therapy with warfarin or equivalent vitamin K antagonists; requires treatment with potent CYP3A4/5 inhibitors.
• Requires long-term use of dexamethasone ≥4mg/day or equivalent doses of corticosteroid formulations.
• Requires treatment with immunosuppressive agents, including cyclosporine A, tacrolimus, and sirolimus. Patients must discontinue the use of immunosuppressive agents 28 days before receiving study medication.