{ "id": "epzb8134b7", "slug": "chlorambucil-and-obinutuzumab-regimen", "title": "Chlorambucil and obinutuzumab regimen", "updated": "2026-10-15", "topic_path": [ { "id": "life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/topics/life" }, { "id": "life.health", "label": "Human health and medicine", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health" }, { "id": "life.health.medicines", "label": "Medicines and therapeutics", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.medicines" }, { "id": "life.health.medicines.cancer-chemotherapy", "label": "Cancer chemotherapy and regimens", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.medicines.cancer-chemotherapy" }, { "id": "life.health.medicines.cancer-chemotherapy.immunotherapy-and-immunochemotherapy", "label": "Immunotherapy and immunochemotherapy", "api_url": "https://www.edgepedia.org/api/v1/topics/life.health.medicines.cancer-chemotherapy.immunotherapy-and-immunochemotherapy" } ], "geo": [ { "id": "geo.nongeo.t2001.life.health.medicines.cancer-chemotherapy", "label": "Non-geographic · 2001 to 2020: Cancer chemotherapy and regimens", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t2001.life.health.medicines.cancer-chemotherapy", "path": [ { "id": "geo.nongeo", "label": "Non-geographic", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo" }, { "id": "geo.nongeo.t2001", "label": "Non-geographic · 2001 to 2020", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t2001" }, { "id": "geo.nongeo.t2001.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t2001.life" }, { "id": "geo.nongeo.t2001.life.health", "label": "Human health and medicine", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t2001.life.health" }, { "id": "geo.nongeo.t2001.life.health.medicines", "label": "Medicines and therapeutics", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t2001.life.health.medicines" }, { "id": "geo.nongeo.t2001.life.health.medicines.cancer-chemotherapy", "label": "Cancer chemotherapy and regimens", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.nongeo.t2001.life.health.medicines.cancer-chemotherapy" } ] } ], "excerpt": "The chlorambucil and obinutuzumab regimen is a chemoimmunotherapy combination pairing oral chlorambucil with the anti-CD20 antibody obinutuzumab, approved in 2013 for previously untreated chronic lymphocytic leukemia.", "snippet": "The chlorambucil and obinutuzumab regimen is a chemoimmunotherapy combination pairing oral chlorambucil with the anti-CD20 antibody obinutuzumab, approved in 2013 for previously untreated chronic lymphocytic leukemia.", "node": "life.health.medicines.cancer-chemotherapy.immunotherapy-and-immunochemotherapy", "markdown": "# Chlorambucil and obinutuzumab regimen\n\nThe chlorambucil and obinutuzumab regimen is a chemoimmunotherapy combination that pairs the oral agent chlorambucil with the anti-CD20 monoclonal antibody obinutuzumab, given over six 28-day cycles for previously untreated chronic lymphocytic leukemia (CLL) in patients with coexisting conditions.[1](https://doi.org/10.1056/nejmoa1313984) The US Food and Drug Administration approved the combination in November 2013 based on the CLL11 trial,[2](https://www.cancer.gov/types/leukemia/research/obinutuzumab-chlorambucil-cll) and NICE recommends it for adults whose comorbidities make full-dose fludarabine-based therapy unsuitable.[3](https://www.nice.org.uk/guidance/ta343/resources/obinutuzumab-in-combination-with-chlorambucil-for-untreated-chronic-lymphocytic-leukaemia-pdf-82602606162373) Since the arrival of BTK and BCL-2 inhibitors, national guidelines updated from 2023 through 2025 in France, Germany, and the US consider chemoimmunotherapy a treatment option in only exceptional cases.[4](https://www.nature.com/articles/s41408-025-01434-2)\n\n| Key fact | Detail |\n|---|---|\n| Indication | Previously untreated CLL in comorbid or unfit patients (CIRS score >6 or creatinine clearance 30–69 mL/min)[1](https://doi.org/10.1056/nejmoa1313984) |\n| Schedule | Six 28-day cycles; chlorambucil 0.5 mg/kg orally on days 1 and 15; obinutuzumab 1,000 mg IV on days 1, 8, and 15 of cycle 1 and day 1 of cycles 2–6[1](https://doi.org/10.1056/nejmoa1313984) |\n| Efficacy (CLL11) | Median PFS 26.7 vs 11.1 months with chlorambucil alone (HR 0.18); overall survival HR 0.41[1](https://doi.org/10.1056/nejmoa1313984) |\n| Infusion reactions | Grade 3–4 reactions in 20% of patients during the first obinutuzumab infusion, none during subsequent infusions[1](https://doi.org/10.1056/nejmoa1313984) |\n| Infections | Grade 3–5 infection rates of 11–14%, not significantly different among treatment groups[1](https://doi.org/10.1056/nejmoa1313984) |\n| Current position | Displaced by BTK inhibitors and venetoclax-based combinations; reserved for exceptional cases in 2023–2025 guidelines[4](https://www.nature.com/articles/s41408-025-01434-2) |\n\n## How it works\n\nObinutuzumab (GA101) is a humanized, glycoengineered type 2 antibody against CD20. In preclinical studies it showed superior efficacy to rituximab by inducing direct cell death and enhanced antibody-dependent cellular cytotoxicity (ADCC), with less complement-dependent cytotoxicity (CDC).[1](https://doi.org/10.1056/nejmoa1313984) Mechanistically, type II antibodies such as obinutuzumab do not localize the antibody–antigen complex into lipid rafts and therefore induce CDC that is 10- to 100-fold weaker than with the type I antibodies rituximab or [ofatumumab](https://www.edgepedia.org/ofatumumab).[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC5279834/) Their direct killing runs through homotypic aggregation: antibody-driven clustering of malignant B cells followed by nonapoptotic, caspase-independent death in which lysosomes release enzymes including cathepsin B, without involvement of Bcl-2.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC5279834/) Reduced FcγRIIb-mediated CD20 internalization increases the capacity to bind and activate natural killer cells, strengthening ADCC and antibody-dependent phagocytosis.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC5279834/)\n\nChlorambucil is administered orally, and the clinical rationale for the combination rests on the CLL11 results: adding obinutuzumab cut the risk of progression or death by 82% versus chlorambucil alone (HR 0.18), and obinutuzumab–chlorambucil also outperformed rituximab–chlorambucil (median PFS 26.7 vs 16.3 months).[1](https://doi.org/10.1056/nejmoa1313984)\n\n## How it is done\n\nTreatment comprises six 28-day cycles.[6](https://www.northerncanceralliance.nhs.uk/wp-content/uploads/2018/11/obinutuzumab-chlorambucil-Previously-untreated-CLL-CRP15-H047-v1.2.pdf) [Chlorambucil](https://www.edgepedia.org/chlorambucil) is given orally at 0.5 mg/kg on days 1 and 15 of each cycle.[1](https://doi.org/10.1056/nejmoa1313984) In CLL11, obinutuzumab was given at 1,000 mg intravenously on days 1, 8, and 15 of cycle 1, and day 1 of cycles 2 through 6; after a protocol amendment, the first infusion was administered over 2 days.[1](https://doi.org/10.1056/nejmoa1313984) The FDA label formalizes this split as 100 mg on day 1 and 900 mg on day 2 of cycle 1, then 1,000 mg on days 8 and 15 of cycle 1 and 1,000 mg on day 1 of cycles 2–6.[7](https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/125486s040lbl.pdf)\n\nBecause obinutuzumab carries a higher rate of infusional toxicity than rituximab, especially on doses 1 and 2, premedication requires methylprednisolone rather than hydrocortisone, and the first dose is given as a divided dose on days 1 and 2.[8](https://gmcancer.org.uk/wp-content/uploads/2022/01/4cll-guidelines_v4.0-feb-2019.pdf) [Premedication](https://www.edgepedia.org/premedication) with a glucocorticoid, acetaminophen, and an antihistamine is given before the first two doses, and tumor lysis prophylaxis includes antihyperuricemic therapy 12–24 hours before starting plus adequate hydration.[9](https://ascopost.com/issues/december-1-2013/obinutuzumab-in-previously-untreated-chronic-lymphocytic-leukemia/) TLS precautions apply to patients with high tumor burden, a circulating lymphocyte count above 25 × 10⁹/L, or creatinine clearance below 70 mL/min.[6](https://www.northerncanceralliance.nhs.uk/wp-content/uploads/2018/11/obinutuzumab-chlorambucil-Previously-untreated-CLL-CRP15-H047-v1.2.pdf) For neutropenia, the BC Cancer protocol caps chlorambucil at 0.8 mg/kg every 2 weeks, allows escalation by 0.1 mg/kg if the ANC exceeds 3.5 × 10⁹/L, and adjusts the dose to keep the neutrophil count above 1.2 × 10⁹/L.[10](https://www.bccancer.bc.ca/chemotherapy-protocols-site/Documents/Lymphoma-Myeloma/LYOBCHLOR_Protocol.pdf)\n\n## Origin\n\nThe regimen was evaluated in the CLL11 trial (ClinicalTrials.gov NCT01010061), funded by F. Hoffmann–La Roche, which randomized 781 previously untreated CLL patients with a CIRS score above 6 or a creatinine clearance of 30–69 mL/min to chlorambucil alone, obinutuzumab–chlorambucil, or rituximab–chlorambucil.[1](https://doi.org/10.1056/nejmoa1313984) The primary report, \"Obinutuzumab plus Chlorambucil in Patients with CLL and Coexisting Conditions,\" was published in the New England Journal of Medicine in 2014 by Valentin Goede and colleagues.[1](https://doi.org/10.1056/nejmoa1313984) On November 1, 2013, obinutuzumab (Gazyva) was approved in combination with chlorambucil for previously untreated CLL.[9](https://ascopost.com/issues/december-1-2013/obinutuzumab-in-previously-untreated-chronic-lymphocytic-leukemia/)\n\n## Variants\n\nObinutuzumab has been combined with backbones other than chlorambucil. In the GALLIUM study (NCT01332968) in 1,202 previously untreated follicular lymphoma patients, obinutuzumab plus CHOP, CVP, or bendamustine prolonged investigator-assessed PFS versus rituximab plus chemotherapy (HR 0.68; 95% CI 0.54–0.87; P = .0016) after 41.1 months of median follow-up, with consistent results across backbones.[11](https://ascopubs.org/doi/10.1200/JCO.2017.76.8960) GALLIUM dosing differs from the CLL regimen: obinutuzumab 1,000 mg on days 1, 8, and 15 of cycle 1 and day 1 of subsequent cycles for six to eight cycles, with 2 years of antibody maintenance for responding patients.[11](https://ascopubs.org/doi/10.1200/JCO.2017.76.8960)\n\nThe CLL regimen itself is defined by fitness criteria. The CLL11 population (CIRS >6 or creatinine clearance 30–69 mL/min) defined the comorbid group for obinutuzumab–chlorambucil.[1](https://doi.org/10.1056/nejmoa1313984) Trial patients had a median age of 73 years, creatinine clearance of 62 mL/min, and CIRS score of 8 at baseline.[1](https://doi.org/10.1056/nejmoa1313984)\n\n## Applications\n\nAt approval, the regimen served comorbid, previously untreated patients for whom intensive chemoimmunotherapy was unsuitable.[2](https://www.cancer.gov/types/leukemia/research/obinutuzumab-chlorambucil-cll) NICE recommends it for adults with untreated CLL whose comorbidities make full-dose fludarabine-based therapy unsuitable, only if bendamustine-based therapy is not suitable and a patient-access-scheme discount applies.[3](https://www.nice.org.uk/guidance/ta343/resources/obinutuzumab-in-combination-with-chlorambucil-for-untreated-chronic-lymphocytic-leukaemia-pdf-82602606162373) NICE reported CLL11 stage 1 PFS as 29.9 versus 11.1 months (HR 0.19) against chlorambucil and stage 2 PFS as 29.2 versus 15.4 months (HR 0.41) against rituximab–chlorambucil; the NEJM primary report gives 26.7 months for the obinutuzumab arm, a discrepancy between the two published presentations of the same trial.[1](https://doi.org/10.1056/nejmoa1313984) • [3](https://www.nice.org.uk/guidance/ta343/resources/obinutuzumab-in-combination-with-chlorambucil-for-untreated-chronic-lymphocytic-leukaemia-pdf-82602606162373) In real-world practice, the Czech GO-CLL EAR cohort found median event-free survival of 49.0 months for obinutuzumab–chlorambucil versus 20.3 months for rituximab–chlorambucil and 37.0 months for bendamustine–rituximab, with grade ≥3 neutropenia in 43%, 31%, and 49% respectively.[12](https://www.muni.cz/en/research/publications/1673757)\n\n## Limitations and alternatives\n\nThe regimen's main toxicities are infusion reactions and cytopenias. In CLL11, grade 3 or 4 infusion-related reactions occurred in 20% of patients during the first obinutuzumab infusion, with none during subsequent infusions and no deaths from infusion reactions; tumor lysis syndrome was reported in 15 patients and resolved in all cases.[1](https://doi.org/10.1056/nejmoa1313984) In ELEVATE-TN, grade ≥3 neutropenia occurred in 41% of obinutuzumab–chlorambucil patients and all-grade infusion reactions in 40%.[13](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2820%2930262-2/abstract)\n\nHead-to-head trials in the same unfit population now favor targeted regimens. In GLOW, fixed-duration ibrutinib–venetoclax gave 42-month PFS of 74.6% versus 24.8% for chlorambucil–obinutuzumab (HR 0.214), with 15 versus 30 deaths.[14](https://www.thelancet.com/article/S1470-2045%2823%2900452-7/abstract) In iLLUMINATE, [ibrutinib plus obinutuzumab](https://www.edgepedia.org/ibrutinib-plus-obinutuzumab) improved PFS over chlorambucil plus obinutuzumab (median not reached vs 22 months; HR 0.25), with undetectable MRD in 38% versus 25%.[15](https://pmc.ncbi.nlm.nih.gov/articles/PMC9425310/) In ELEVATE-TN, 24-month PFS was 93% with acalabrutinib–obinutuzumab and 87% with acalabrutinib alone versus 47% with obinutuzumab–chlorambucil.[13](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2820%2930262-2/abstract) CLL14 used chlorambucil–obinutuzumab as the comparator for venetoclax–obinutuzumab in the CIRS >6 or creatinine clearance below 70 mL/min population.[16](https://www.nejm.org/doi/full/10.1056/NEJMoa1815281) In a subsequent interim analysis of 909 patients, 3-year PFS was 81.1% with venetoclax–obinutuzumab, 79.4% with venetoclax–ibrutinib, and 81.0% with ibrutinib, with post-treatment MRD undetectable in 73.3%, 47.2%, and 0% respectively.[17](https://pubmed.ncbi.nlm.nih.gov/41358601/) Against rituximab–chlorambucil, the obinutuzumab combination remains the stronger chemoimmunotherapy option (PFS HR 0.44 vs chlorambucil for rituximab–chlorambucil, versus 0.18 for obinutuzumab–chlorambucil).[1](https://doi.org/10.1056/nejmoa1313984)\n\n## References\n\n1. [Valentin Goede and colleagues (2014). Obinutuzumab plus Chlorambucil in Patients with CLL and Coexisting Conditions. New England Journal of Medicine.](https://doi.org/10.1056/nejmoa1313984)\n2. [Obinutuzumab Plus Chlorambucil for Patients with Chronic Lymphocytic Leukemia and Comorbidities - NCI](https://www.cancer.gov/types/leukemia/research/obinutuzumab-chlorambucil-cll)\n3. [NICE TA343: Obinutuzumab in combination with chlorambucil for untreated chronic lymphocytic leukaemia](https://www.nice.org.uk/guidance/ta343/resources/obinutuzumab-in-combination-with-chlorambucil-for-untreated-chronic-lymphocytic-leukaemia-pdf-82602606162373)\n4. [First-line treatment for CLL in the era of targeted therapy | Blood Cancer Journal](https://www.nature.com/articles/s41408-025-01434-2)\n5. [Obinutuzumab in chronic lymphocytic leukemia: design, development and place in therapy](https://pmc.ncbi.nlm.nih.gov/articles/PMC5279834/)\n6. [Northern Cancer Alliance: Obinutuzumab and Chlorambucil for CLL](https://www.northerncanceralliance.nhs.uk/wp-content/uploads/2018/11/obinutuzumab-chlorambucil-Previously-untreated-CLL-CRP15-H047-v1.2.pdf)\n7. [FDA Prescribing Information for Gazyva (obinutuzumab), revised 12/2025](https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/125486s040lbl.pdf)\n8. [GM Cancer Alliance Guidelines for the Management of CLL (v4.0, Feb 2019)](https://gmcancer.org.uk/wp-content/uploads/2022/01/4cll-guidelines_v4.0-feb-2019.pdf)\n9. [Obinutuzumab in Previously Untreated Chronic Lymphocytic Leukemia - The ASCO Post](https://ascopost.com/issues/december-1-2013/obinutuzumab-in-previously-untreated-chronic-lymphocytic-leukemia/)\n10. [BC Cancer Protocol Summary: obinutuzumab and chlorambucil for previously untreated CLL/SLL](https://www.bccancer.bc.ca/chemotherapy-protocols-site/Documents/Lymphoma-Myeloma/LYOBCHLOR_Protocol.pdf)\n11. [Immunochemotherapy With Obinutuzumab or Rituximab for Previously Untreated Follicular Lymphoma in the GALLIUM Study](https://ascopubs.org/doi/10.1200/JCO.2017.76.8960)\n12. [Real-world GO-CLL EAR study (Czech CLL Study Group): G-Clb vs R-Clb vs BR frontline](https://www.muni.cz/en/research/publications/1673757)\n13. [abstract (thelancet.com)](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2820%2930262-2/abstract)\n14. [abstract (thelancet.com)](https://www.thelancet.com/article/S1470-2045%2823%2900452-7/abstract)\n15. [First-line treatment of CLL with ibrutinib plus obinutuzumab versus chlorambucil plus obinutuzumab: final analysis of the phase III iLLUMINATE trial](https://pmc.ncbi.nlm.nih.gov/articles/PMC9425310/)\n16. [Venetoclax and Obinutuzumab in Patients with CLL and Coexisting Conditions (CLL14)](https://www.nejm.org/doi/full/10.1056/NEJMoa1815281)\n17. [Fixed-Duration versus Continuous Treatment for Chronic Lymphocytic Leukemia](https://pubmed.ncbi.nlm.nih.gov/41358601/)\n\n---\n*Topic: Encyclopedia › Life and health › Human health and medicine › Medicines and therapeutics › Cancer chemotherapy and regimens › Immunotherapy and immunochemotherapy*\n\n*Initially written Sep 29, 2026 · Edited: Oct 15, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n", "same_as": [], "url": "https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen", "markdown_url": "https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen.md", "license": { "name": "Edgepedia Community License 1.0", "url": "https://www.edgepedia.org/edgepedia/license", "summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.", "spdx": "LicenseRef-Edgepedia-Community-1.0" }, "credit": "\"Chlorambucil and obinutuzumab regimen\", Edgepedia (EdgeChat), https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen. Edgepedia Community License 1.0.", "credit_md": "\"[Chlorambucil and obinutuzumab regimen](https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen](https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"Chlorambucil and obinutuzumab regimen\", Edgepedia (EdgeChat), https://www.edgepedia.org/chlorambucil-and-obinutuzumab-regimen. Edgepedia Community License 1.0.", "speakable": "The chlorambucil and obinutuzumab regimen is a chemoimmunotherapy combination pairing oral chlorambucil with the anti-CD20 antibody obinutuzumab, approved in 2013 for previously untreated chronic lymphocytic leukemia." }