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New CDK inhibitors that also target CDK2 show great activity in models resistant to current CDK4/6 agents. Instead of being reserved for later use, they are already being tested in frontline trials. The strategy, similar to that of ALK inhibitors in lung cancer, is that using the best drug first may prevent or significantly delay the onset of resistance.

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The VICTORIA-1 trial found that re-introducing palbociclib in a triplet with gedatolisib was effective, even in patients who had just progressed on palbociclib. This suggests that gedatolisib targets and overcomes the primary resistance mechanism to the CDK4/6 inhibitor, re-sensitizing the cancer to it.

The novel DiviTum TKA assay measures cell proliferation in real-time. Patterns of TKA level suppression, rebound, or lack of suppression within the first month of CDK4/6 inhibitor therapy strongly predict a patient's long-term progression-free survival, offering an early look at treatment efficacy.

A patient's time to progression on first-line CDK4/6 inhibitor therapy acts as an informal biomarker. A shorter duration, such as 14 months, is viewed by experts as "not so great" and indicates a degree of underlying endocrine resistance that influences subsequent treatment strategies.

The ELEGANT trial uses a "switch strategy," introducing elicestrin only after 2-5 years of standard therapy. This design pragmatically adapts to the evolving clinical landscape where CDK4/6 inhibitors are now standard initial treatment, ensuring the trial's relevance by testing the drug in a post-CDK4/6 inhibitor setting.

While TROP2-ADCs are currently approved for later-line lung cancer treatment, active clinical trials are already evaluating them as a potential replacement for traditional chemotherapy in the first-line setting. This represents a significant strategic ambition to shift the entire treatment paradigm for newly diagnosed patients with both non-small cell and small cell lung cancer.

Three major trials (RIGHT Choice, PADMA, OMBRE) definitively show that starting with a CDK4/6 inhibitor plus endocrine therapy is superior to upfront chemotherapy for newly diagnosed, symptomatic metastatic breast cancer. This approach provides better progression-free survival without the toxicity of chemotherapy and, critically, does not result in a slower time to response.

The long-standing platinum doublet backbone for frontline SCLC may soon be challenged. The high efficacy of novel agents like antibody-drug conjugates and bispecific antibodies in later lines is prompting trials that consider moving them into the first-line setting, a strategy previously considered "unthinkable."

Data from the MONARCH-E and NATALY trials show that the benefit of adjuvant CDK4/6 inhibitors like abemaciclib and ribociclib persists and even increases after patients complete their 2-3 year treatment course. This sustained "carryover effect" suggests a lasting impact on disease biology rather than just temporary suppression.

Before CDK inhibitors, second-line fulvestrant provided ~12 months of progression-free survival (PFS). Now, after progression on a CDK inhibitor, PFS on fulvestrant is merely 2-3 months. This demonstrates how a powerful frontline therapy can alter a tumor's genomic structure, making it more virulent and resistant to subsequent standard treatments.

Using a second CDK4/6 inhibitor after progression on a first showed disappointing results in trials like post-MONARCH. However, the EMBER-3 trial's success, combining abemaciclib with the novel SERD imlunestrant, demonstrated robust efficacy. This suggests the choice of endocrine partner is the critical factor for making this sequencing strategy viable.