Relapsed/refractory acute lymphoblastic leukemia remains a challenge in the context of limited access to immunotherapy in developing countries. With such poor 5-year overall survival rates of 10%, the investigators need strategies that surpass the complete response rate achieved in this setting, which does not exceed 60% effectiveness with different regimens, and to eventually transfer patients to hematopoietic stem cell transplantation.

In this context, the investigators are studyng if the use of venetoclax, a BCL2 inhibitor, with the use of a cytochrome p450 inhibitor such as itraconazole, alongside the TACL chemotherapy regimen, which is based on the combination of asparaginase, dexamethasone, bortezomib, vincristine, and mitoxantrone.

Response rates for salvage regimens vary depending on the patient's performance status (suitable or unsuitable for high-intensity chemotherapy), whether the patient is refractory (40%), in early or late first relapse (up to 60%), and in second or later relapse, where complete response rates decrease dramatically (as low as 10% with high-intensity regimens). Post-refractory OS has been reported at 5 months, with an EFS of 4.7 months. For patients in first relapse, the reported studies range from 5.8 months for those receiving salvage chemotherapy alone, increasing to 10 months if they undergo hematopoietic progenitor cell transplantation. For second relapses or relapses after transplantation, OS does not exceed 5 months. For patients who do not receive any treatment, the prognosis is grim, with high mortality within the following months following refractoriness or relapse without any support. 30,31,32

Therefore, it is proposed to increase the complete response rate with a pediatric-inspired chemotherapy regimen in conjunction with a BCL-2 inhibitor, so that patients can be transitioned to allogeneic bone marrow transplantation (the only curative therapy in this context), either after the treatment received or with short-term immunotherapy bridging to transplantation.

The risks associated with conventional salvage chemotherapy for patients with good performance status will not differ significantly from those typically observed in daily clinical practice (see below for the expected description of adverse events), since the basis of therapy remains the TACL regimen. A higher degree of cytopenias, especially neutropenia and thrombocytopenia, can be expected with the addition of a BCL-2 inhibitor.

Salvage chemotherapy will be assigned as follows:

• Venetoclax 100 mg orally every day for 7 days
• Itraconazole 100 mg orally every 12 hours for 7 days
• Vincristine 1.4 mg/m2 intravenously on days 1, 8, 15, and 22
• Mitoxantrone 6 mg/m2 intravenously on day 1
• L-Asparaginase 6,000 IU/m2 intramuscularly on days 5, 7, 9, 11, 13, 16, 18, 20, and 23
• Dexamethasone 20 mg orally from days 1 to 15
• Bortezomib 2 mg subcutaneously on days 1, 4, 8, and 11
• Rituximab 375 mg/m2 intravenously on day 8 for patients with CD20+, more than 20% expression in flow cytometry
• Intrathecal Chemotherapy or CNS (-): Days 8 and 15 or CNS (+): Days 1, 8, 15, and 22

The proposed chemotherapy regimen will be administered orally, intravenously, intramuscularly, and subcutaneously in an outpatient setting on the previously specified days, with appointments scheduled on days 1, 8, 15, and 22 for drug administration on the fifth floor of the University Cancer Center in the Hematology Service area. General patient assessment will be conducted in the ground floor offices of the University Cancer Center's Hematology Service. Any adverse events will be reported by system and grade according to CTCAE.

After completing the salvage chemotherapy regimen, bone marrow aspiration and measurable residual disease will be assessed on day 29 of the cycle, and not beyond day 35.

Inclusion Criteria:

• B-cell or T-cell acute lymphoblastic leukemia.
• Philadelphia chromosome negative
• Relapsed disease after any line of treatment, defined as detection of disease activity at any time after remission
• Refractory disease after first-line treatment, defined as: more than 5% blasts after completion of induction/consolidation by flow cytometry
• Not having included venetoclax in any prior regimen.
• No prior organ damage, defined as the absence of any serious, life-threatening disease prior to the start of treatment.
• Performance status defined by the ECOG scale between 0 and 2.

Exclusion Criteria:

• Isolated CNS relapse.
• Performance status defined by ECOG scale between 3 and 4.
• CTCAE-classified sensory or motor neuropathy of grade 3 or higher.
• History of hypersensitivity or intolerance to the drugs included in the regimen.
• Prior organ damage, defined as the presence of any serious, life-threatening illness prior to the start of treatment.