Table 3.

Summary and interpretation of BSNV reported in this dataset.

Mutation	Evidence from this study	Published in vitro data	Published in vivo data#
Emerging BSNV-harbouring clones, associated with resistance. Suggests clonal selection associated with resistance. Likely clinically relevant.
E459K	Positive clonal selection associated with treatment resistance in 1 patient receiving 80 mg daily, but negative selection against E459K-harbouring clone in 1 patient receiving 240 mg daily.	Modestly increased IC50 ~ 5 fold [1, 11].	Present in baseline sample of 1 patient in phase 3 study (isolated E459K) who failed to achieve MMR at week 24 and discontinued treatment, no clonal dynamic reported [9].
F317L	Positive clonal selection associated with treatment resistance in 1 patient receiving 80 mg daily, no data at higher doses.	Increased IC50 ~ 20 to >300 fold [12, 25].	Identified in 3 patients in phase 3 study: Isolated F317L present at baseline in 1 patient who failed to MMR at week 24 and discontinued treatment; Present at baseline in combination/compound (F317L/L248V) in 1 patient who failed to achieve MMR at week 24 and discontinued treatment; Emergent combination/compound (F317L/E355G) in 1 patient who failed to achieve MMR at week 24 and discontinued treatment, no clonal dynamic reported [9]. Present in dominant clone (VAF 100% at initiation and VAF 99% at follow-up) in 1 patient who achieved MMR, no dose information reported [12].
F486S	Positive clonal selection associated with treatment resistance in 1 patient receiving 80 mg daily, no data at higher doses.	No data.	No data on isolated F486S. Present in baseline sample in combination/compound with Y253H in 1 patient in phase 3 study who failed MMR at week 24 and discontinued treatment, no clonal dynamics reported [9].
F359I	Positive clonal selection associated with treatment resistance in 1 patient receiving 240 mg daily, no data at higher doses.	Increased IC50 > 500 fold [12].	Clonal selection for dominant clone harbouring isolated F359I in one patient (undetectable at baseline to VAF 99%) and F359V in one patient (VAF 79% at baseline to 98%) emergent from background populations harbouring multiple mutations, associated with treatment failure in both patients receiving doses up to 400 mg daily. Clonal selection in association with other BSNV in 1 patient (T315I, VAF 29% alone at baseline to F359I, VAF 46%, T315I, VAF 40%, A433D, VAF 11%, P112S, VAF 3%) [12]. Isolated F359C and F359V in baseline samples of 1 and 3 patients respectively in phase 3 study, all of whom failed to achieve MMR at 24 weeks and discontinued treatment, no clonal dynamics reported [9]. F359V present in 1 patient on compassionate use programme who failed to achieve CCyR (80 mg daily), no clonal dynamics reported [22].
Compound T315I/M351T	Positive clonal selection associated with treatment resistance in 1 patient receiving 400 mg daily.	Increased IC50 > 500 fold [12].	No data.
BSNV stably present in a dominant clone, associated with resistance. May represent BSNV-mediated or non-BSNV mediated mechanism of resistance with co-existing BSNV passenger mutations. Possibly clinically relevant.
F359V	Resistance with ongoing clonal dominance in 1 patient receiving 80 mg daily.	Increased IC50, ~20- to >500-fold [1, 11, 12, 25].	Refer to F359I above.
Compound G250E/F486S	Resistance with ongoing clonal dominance in 1 patient receiving 80 mg daily.	No compound data; isolated G250E modestly increased IC50 ~ 1.5- to 5-fold [12, 25]; isolated F486S no data.	No data on compound mutations. See F486S above and G250E below for isolated mutation data.
T315I with low-level H396R	Resistance with unchanged clone size in 1 patient receiving 400 mg daily.	Increased IC50 > 500-fold in compound [12]; Isolated T315I increased IC50 ~ 8–12-fold [1, 11, 12]; Isolated H396R increased IC50 ~ 16-fold [12].	No data on compound mutations. Established resistance of T315I alone to standard doses, clinical responses achieved on 200 mg BD [8, 13]. Evidence of clonal selection on standard dose, overcome with higher dose in non-responding patients [12]. No data on isolated H396R.
Emerging BSNV-harbouring clones with ongoing clinically meaningful response. Indicates clonal selection, but insufficient resistance to preclude clinical response. Unknown clinical relevance.
I502F	Positive clonal selection in 1 patient receiving 80 mg daily, who achieved sustained CCyR.	No data on I502F; Increased IC50 for I502L ~ 50-fold [1].	No data on I502F. Clinical progression in 1 patient in phase 1 study, in AP associated with emergence of I502L (VAF 87.8%), V468F (VAF 11.9%) and E355G (VAF 1.1%) [8].
T315I	Positive clonal selection at 400 mg daily, but achieved deep molecular responses in 3 patients.	Increased IC50 ~ 8-12-fold [1, 11, 12, 25].	Established resistance of T315I to standard doses, clinical responses achieved on 200 mg BD [8, 13]. Evidence of clonal selection on standard dose, overcome with higher dose in non-responding patients [12].
Low-level variants associated with resistance. Potentially passenger BSNV in the context of non-BSNV-mediated resistance. Unknown clinical relevance.
Q252H	Emergence at low-level (3%) associated with treatment resistance in 1 patient receiving 400 mg daily.	Increased IC50 ~ 4-18-fold [1, 11, 12].	No data.
V338A	Emergence at low-level (4%) associated with treatment resistance in 1 patient receiving 80 mg daily.	No data.	No data.
V299L	Persistence of low-level clone associated with treatment resistance in 1 patient receiving 80 mg daily (3% at imitation, 4% at cessation)	Modestly increased IC50 ~ 10-fold [1].	No data in chronic phase. Present in 1 patient on in phase 1 study, in AP treated with 40 mg BD who progressed, without evidence of clonal selections/dominance [8].
BSNV-harbouring clones negatively selected against. Suggestive of sensitivity to asciminib. Possibly clinically relevant.
E255V*	Negatively selected against despite treatment resistance in 1 patient receiving 80 mg daily.	Modestly increased IC50 ~ 3–4-fold [1, 11, 12].	E255V and E255K present in baseline samples in 1 and 2 patients respectively in phase 3 study who achieved MMR at week 24 and continued treatment, no clonal dynamics reported [9]. E255K present in dominant clone (VAF 100%) at baseline in 1 patient in phase 1 study who achieved MMR on 40 mg BD but subsequently lost response with emergence of G463S mutation (VAF not reported) [8]. E255K presented in combination with T315I in 1 patient on compassionate use programme who failed to achieve a response on 400 mg daily, no clonal dynamics reported [21].
G250E*	Negatively selected against despite treatment resistance in 1 patient receiving 240 mg daily.	Modestly increased IC50 ~ 5–6-fold [12, 25].	Isolated G250E in baseline sample of 1 patient in phase 3 study who failed to achieve MMR at week 24 but continued treatment, and emergent in 1 patient in phase 3 study who achieved MMR at week 24 and continued treatment, no clonal dynamics reported [9]. Present in 1 patient on compassionate use programme achieving MR4 receiving 80 mg daily, no clonal dynamics reported [22].
Y253H*	Negatively selected against despite treatment resistance in 1 patient receiving 240 mg daily.	Modestly increased IC50 ~ 2–6-fold [1, 11, 12, 25].	Isolated Y253H in baseline sample of 1 patient who achieved MMR at week 24 and continued treatment, and emergent in 1 patient in who failed to achieve MMR at week 24 and discontinued treatment in phase 3 study, no clonal dynamics reported [9]. Isolated Y253H in 1 patient on compassionate use programme achieving CCyR on 80 mg daily, use no clonal dynamics reported [22]. Present in combination with T315I in 1 patient on compassionate use programme with AP who failed to achieve a response on 200 mg BD [21].
BSNV identified in the study, insufficient data to classify. Unable to classify.
M244V*,**	Positive clonal selection in combination with P465L and A337T in 1 patient with haematological response only.	Increased IC50 ~ 20-fold [25]	Associated with treatment resistance and emergence/clonal dominance in 4 patients, some receiving up to 200 mg BD [25]. Present in baseline sample of 1 patient in phase 1 study who developed progressive disease on treatment, no dose or clonal dynamics reported [8]. Present as isolated M244V in 1 patient who failed to achieve CCyR on 80 mg daily, and in combination with F317L and E255K in 2 further patients, one in AP who failed to achieve CCyR on 200 mg daily, and one in CP who achieved CCyR on 80 mg daily, on compassionate use programme, no clonal dynamics reported [22]. Present in combination with a F317L in 1 patient on compassionate use programme achieving CCyR on 40 mg BD, no clonal dynamics reported [21]
P465L*,**	Positive clonal selection in combination with M244V and A337T in 1 patient with haematological response only.	No data in P465L; P465S associated with increased IC50 > 500-fold [12]	No data on P465L; Emergent P465S mutation (VAF8%) in combination with G109D (VAF3.3%) and T315I (VAF100%) in 1 patient in phase 1 study on asciminib treatment with up to 200 mg BD and no notable response [8].
A337T*,**	Positive clonal selection at low level (VAF 3%) in combination with M244V and P465L in 1 patient with haematological response only.	No data in A337T; A337V increased IC50 > 500-fold [1, 12]	Emergent A337T mutation (VAF 37%) in combination with G463D (VAF 8.7%) and Y115N (VAF 5%) with re-existing T315I (VAF 40.4%) in 1 patient on up to 200 mg BD in phase 1 study [8]. Present at low level without evidence of clonal selection patients in doses up to 200 mg BD [12]

BSNV, BCR::ABL1 single nucleotide variant, mg milligrams, IC50 half maximal inhibitory concentration, CCyR complete cytogenetic response (BCR::ABL1 IS level ≤ 1%), MMR major molecular response (BCR::ABL1 IS level ≤ 0.1%), MR4, BCR::ABL1 IS level ≤ 0.01% IS, VAF variant allele fraction, CP chronic phase, AP accelerated phase, IS international scale. * Reported in the context of more than a BSNV, unable to exclude compound clones/BSNV interaction, ** Unable to differentiate co-existing or compound state (M244V (19%), P465L (19%), A337T (3%)), ± Note that IC50 > 1 but ≤10 fold more than non-mutant BCR::ABL1 have been defined as modestly increased, IC50 > 10 are defined as increased, # Unless otherwise stated, in vivo data reports to chronic phase patients receiving standard dose regimens (80 mg daily).